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.

Errors in quantitative backscattered electron analysis of bone standardized by energy-dispersive x-ray spectrometry.

PubMed

Vajda, E G; Skedros, J G; Bloebaum, R D

1998-10-01

Backscattered electron (BSE) imaging has proven to be a useful method for analyzing the mineral distribution in microscopic regions of bone. However, an accepted method of standardization has not been developed, limiting the utility of BSE imaging for truly quantitative analysis. Previous work has suggested that BSE images can be standardized by energy-dispersive x-ray spectrometry (EDX). Unfortunately, EDX-standardized BSE images tend to underestimate the mineral content of bone when compared with traditional ash measurements. The goal of this study is to investigate the nature of the deficit between EDX-standardized BSE images and ash measurements. A series of analytical standards, ashed bone specimens, and unembedded bone specimens were investigated to determine the source of the deficit previously reported. The primary source of error was found to be inaccurate ZAF corrections to account for the organic phase of the bone matrix. Conductive coatings, methylmethacrylate embedding media, and minor elemental constituents in bone mineral introduced negligible errors. It is suggested that the errors would remain constant and an empirical correction could be used to account for the deficit. However, extensive preliminary testing of the analysis equipment is essential.

Enhanced production of low energy electrons by alpha particle impact

PubMed Central

Kim, Hong-Keun; Titze, Jasmin; Schöffler, Markus; Trinter, Florian; Waitz, Markus; Voigtsberger, Jörg; Sann, Hendrik; Meckel, Moritz; Stuck, Christian; Lenz, Ute; Odenweller, Matthias; Neumann, Nadine; Schössler, Sven; Ullmann-Pfleger, Klaus; Ulrich, Birte; Fraga, Rui Costa; Petridis, Nikos; Metz, Daniel; Jung, Annika; Grisenti, Robert; Czasch, Achim; Jagutzki, Ottmar; Schmidt, Lothar; Jahnke, Till; Schmidt-Böcking, Horst; Dörner, Reinhard

2011-01-01

Radiation damage to living tissue stems not only from primary ionizing particles but to a substantial fraction from the dissociative attachment of secondary electrons with energies below the ionization threshold. We show that the emission yield of those low energy electrons increases dramatically in ion–atom collisions depending on whether or not the target atoms are isolated or embedded in an environment. Only when the atom that has been ionized and excited by the primary particle impact is in immediate proximity of another atom is a fragmentation route known as interatomic Coulombic decay (ICD) enabled. This leads to the emission of a low energy electron. Over the past decade ICD was explored in several experiments following photoionization. Most recent results show its observation even in water clusters. Here we show the quantitative role of ICD for the production of low energy electrons by ion impact, thus approaching a scenario closer to that of radiation damage by alpha particles: We choose ion energies on the maximum of the Bragg peak where energy is most efficiently deposited in tissue. We compare the electron production after colliding He+ ions on isolated Ne atoms and on Ne dimers (Ne2). In the latter case the Ne atom impacted is surrounded by a most simple environment already opening ICD as a deexcitation channel. As a consequence, we find a dramatically enhanced low energy electron yield. The results suggest that ICD may have a significant influence on cell survival after exposure to ionizing radiation. PMID:21730184

Electron heating and energy inventory during asymmetric reconnection in a laboratory plasma

NASA Astrophysics Data System (ADS)

Yoo, J.; Na, B.; Jara-Almonte, J.; Yamada, M.; Ji, H.; Roytershteyn, V.; Argall, M. R.; Fox, W.; Chen, L. J.

2017-12-01

Electron heating and the energy inventory during asymmetric reconnection are studied in the Magnetic Reconnection Experiment (MRX) [1]. In this plasma, the density ratio is about 8 across the current sheet. Typical features of asymmetric reconnection such as the large density gradients near the low-density-side separatrices, asymmetric in-plane electric field, and bipolar out-of-plane magnetic field are observed. Unlike the symmetric case [2], electrons are also heated near the low-density-side separatrices. The measured parallel electric field may explain the observed electron heating. Although large fluctuations driven by lower-hybrid drift instabilities are also observed near the low-density-side separatrices, laboratory measurements and numerical simulations reported here suggest that they do not play a major role in electron energization. The average electron temperature increase in the exhaust region is proportional to the incoming magnetic energy per an electron/ion pair but exceeds the scaling of the previous space observations [3]. This discrepancy is explained by differences in the boundary condition and system size. The profile of electron energy gain from the electric field shows that there is additional electron energy gain associated with the electron diamagnetic current besides a large energy gain near the X-line. This additional energy gain increases electron enthalpy, not the electron temperature. Finally, a quantitative analysis of the energy inventory during asymmetric reconnection is conducted. Unlike the symmetric case where the ion energy gain is about twice more than the electron energy gain [4], electrons and ions obtain a similar amount of energy during asymmetric reconnection. [1] J. Yoo et al., accepted for a publication in J. Geophys. Res. [2] J. Yoo et al., Phys. Plasmas 21, 055706 (2014). [3] T. Phan et al., Geophys. Res. Lett. 40, 4475 (2013). [4] M. Yamada et al., Nat. Comms. 5, 4474 (2014).

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

Comparative analysis of characteristic electron energy loss spectra and inelastic scattering cross-section spectra of Fe

NASA Astrophysics Data System (ADS)

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

2016-05-01

The inelastic electron scattering cross section spectra of Fe have been calculated based on experimental spectra of characteristic reflection electron energy loss as dependences of the product of the inelastic mean free path by the differential inelastic electron scattering cross section on the electron energy loss. It has been shown that the inelastic electron scattering cross-section spectra have certain advantages over the electron energy loss spectra in the analysis of the interaction of electrons with substance. The peaks of energy loss in the spectra of characteristic electron energy loss and inelastic electron scattering cross sections have been determined from the integral and differential spectra. It has been shown that the energy of the bulk plasmon is practically independent of the energy of primary electrons in the characteristic electron energy loss spectra and monotonically increases with increasing energy of primary electrons in the inelastic electron scattering cross-section spectra. The variation in the maximum energy of the inelastic electron scattering cross-section spectra is caused by the redistribution of intensities over the peaks of losses due to various excitations. The inelastic electron scattering cross-section spectra have been analyzed using the decomposition of the spectra into peaks of the energy loss. This method has been used for the quantitative estimation of the contributions from different energy loss processes to the inelastic electron scattering cross-section spectra of Fe and for the determination of the nature of the energy loss peaks.

Quantitative Kα line spectroscopy for energy transport in ultra-intense laser plasma interaction

NASA Astrophysics Data System (ADS)

Zhang, Z.; Nishimura, H.; Namimoto, T.; Fujioka, S.; Arikawa, Y.; Nakai, M.; Koga, M.; Shiraga, H.; Kojima, S.; Azechi, H.; Ozaki, T.; Chen, H.; Pakr, J.; Williams, G. J.; Nishikino, M.; Kawachi, T.; Sagisaka, A.; Orimo, S.; Ogura, K.; Pirozhkov, A.; Yogo, A.; Kiriyama, H.; Kondo, K.; Okano, Y.

2012-10-01

X-ray line spectra ranging from 17 to 77 keV were quantitatively measured with a Laue spectrometer, composed of a cylindrically curved crystal and a detector. The absolute sensitivity of the spectrometer system was calibrated using pre-characterized laser-produced x-ray sources and radioisotopes, for the detectors and crystal respectively. The integrated reflectivity for the crystal is in good agreement with predictions by an open code for x-ray diffraction. The energy transfer efficiency from incident laser beams to hot electrons, as the energy transfer agency for Au Kα x-ray line emissions, is derived as a consequence of this work. By considering the hot electron temperature, the transfer efficiency from LFEX laser to Au plate target is about 8% to 10%.

Accurate virus quantitation using a Scanning Transmission Electron Microscopy (STEM) detector in a scanning electron microscope.

PubMed

Blancett, Candace D; Fetterer, David P; Koistinen, Keith A; Morazzani, Elaine M; Monninger, Mitchell K; Piper, Ashley E; Kuehl, Kathleen A; Kearney, Brian J; Norris, Sarah L; Rossi, Cynthia A; Glass, Pamela J; Sun, Mei G

2017-10-01

A method for accurate quantitation of virus particles has long been sought, but a perfect method still eludes the scientific community. Electron Microscopy (EM) quantitation is a valuable technique because it provides direct morphology information and counts of all viral particles, whether or not they are infectious. In the past, EM negative stain quantitation methods have been cited as inaccurate, non-reproducible, and with detection limits that were too high to be useful. To improve accuracy and reproducibility, we have developed a method termed Scanning Transmission Electron Microscopy - Virus Quantitation (STEM-VQ), which simplifies sample preparation and uses a high throughput STEM detector in a Scanning Electron Microscope (SEM) coupled with commercially available software. In this paper, we demonstrate STEM-VQ with an alphavirus stock preparation to present the method's accuracy and reproducibility, including a comparison of STEM-VQ to viral plaque assay and the ViroCyt Virus Counter. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Quantitative characterization of nanoscale polycrystalline magnets with electron magnetic circular dichroism.

PubMed

Muto, Shunsuke; Rusz, Ján; Tatsumi, Kazuyoshi; Adam, Roman; Arai, Shigeo; Kocevski, Vancho; Oppeneer, Peter M; Bürgler, Daniel E; Schneider, Claus M

2014-01-01

Electron magnetic circular dichroism (EMCD) allows the quantitative, element-selective determination of spin and orbital magnetic moments, similar to its well-established X-ray counterpart, X-ray magnetic circular dichroism (XMCD). As an advantage over XMCD, EMCD measurements are made using transmission electron microscopes, which are routinely operated at sub-nanometre resolution, thereby potentially allowing nanometre magnetic characterization. However, because of the low intensity of the EMCD signal, it has not yet been possible to obtain quantitative information from EMCD signals at the nanoscale. Here we demonstrate a new approach to EMCD measurements that considerably enhances the outreach of the technique. The statistical analysis introduced here yields robust quantitative EMCD signals. Moreover, we demonstrate that quantitative magnetic information can be routinely obtained using electron beams of only a few nanometres in diameter without imposing any restriction regarding the crystalline order of the specimen.

A general way for quantitative magnetic measurement by transmitted electrons

NASA Astrophysics Data System (ADS)

Song, Dongsheng; Li, Gen; Cai, Jianwang; Zhu, Jing

2016-01-01

EMCD (electron magnetic circular dichroism) technique opens a new door to explore magnetic properties by transmitted electrons. The recently developed site-specific EMCD technique makes it possible to obtain rich magnetic information from the Fe atoms sited at nonequivalent crystallographic planes in NiFe2O4, however it is based on a critical demand for the crystallographic structure of the testing sample. Here, we have further improved and tested the method for quantitative site-specific magnetic measurement applicable for more complex crystallographic structure by using the effective dynamical diffraction effects (general routine for selecting proper diffraction conditions, making use of the asymmetry of dynamical diffraction for design of experimental geometry and quantitative measurement, etc), and taken yttrium iron garnet (Y3Fe5O12, YIG) with more complex crystallographic structure as an example to demonstrate its applicability. As a result, the intrinsic magnetic circular dichroism signals, spin and orbital magnetic moment of iron with site-specific are quantitatively determined. The method will further promote the development of quantitative magnetic measurement with high spatial resolution by transmitted electrons.

Sterilization of foods with low-energy electrons (``soft-electrons'')

NASA Astrophysics Data System (ADS)

Hayashi, Toru; Takahashi, Yoko; Todoriki, Setsuko

1998-06-01

Electrons with an energy of 300 keV or lower were defined as "Soft-electrons", which showed several advantages over conventional irradiation with gamma-rays or high-energy electrons in decontamination of grains and spices. Energies of electrons necessary to reduce microbial loads to levels lower than 10 CFU/g were 60 keV for brown rice, 75 keV for wheat, 100 keV for white pepper, coriander and basil, 130 keV for buckwheat, 160 keV for rough rice, and 210 keV for black pepper. Electrons with such energies did not significantly influence the quality.

Theoretical modeling of low-energy electronic absorption bands in reduced cobaloximes

DOE PAGES

Bhattacharjee, Anirban; Chavarot-Kerlidou, Murielle; Dempsey, Jillian L.; ...

2014-08-11

Here, we report that the reduced Co(I) states of cobaloximes are powerful nucleophiles that play an important role in the hydrogen-evolving catalytic activity of these species. In this work we have analyzed the low energy electronic absorption bands of two cobaloxime systems experimentally and using a variety of density functional theory and molecular orbital ab initio quantum chemical approaches. Overall we find a reasonable qualitative understanding of the electronic excitation spectra of these compounds but show that obtaining quantitative results remains a challenging task.

Quantitative energy-filtered TEM imaging of interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bentley, J.; Kenik, E.A.; Siangchaew, K.

Quantitative elemental mapping by inner shell core-loss energy-filtered transmission electron microscopy (TEM) with a Gatan Imaging Filter (GIF) interfaced to a Philips CM30 TEM operated with a LaB{sub 6} filament at 300 kV has been applied to interfaces in a range of materials. In sensitized type 304L stainless steel aged 15 h at 600{degrees}C, grain-boundary Cr depletion occurs between Cr-rich intergranular M{sub 23}C{sub 6} particles. Images of net Cr L{sub 23} intensity show segregation profiles that agree quantitatively with focused-probe spectrum-line measurements recorded with a Gatan PEELS on a Philips EM400T/FEG (0.8 nA in 2-nm-diam probe) of the same regions.more » Rare-earth oxide additives that are used for the liquid-phase sintering of Si{sub 3}N{sub 4} generate second phases of complex composition at grain boundaries and edges. These grain boundary phases often control corrosion, crack growth and creep damage behavior. High resolution imaging has been widely and with focused probes can be compromised by beam damage, but elemental mapping by EFTEM appears not to cause appreciable beam damage.« less

Quantitative Probes of Electron-Phonon Coupling in an Organic Charge-Transfer Material

NASA Astrophysics Data System (ADS)

Rury, Aaron; Sorenson, Shayne; Driscoll, Eric; Dawlaty, Jahan

While organic charge transfer (CT) materials may provide alternatives to inorganic materials in electronics and photonics applications, properties central to applications remain understudied in these organic materials. Specifically, electron-phonon coupling plays a pivotal role in electronic applications yet this coupling in CT materials remains difficult to directly characterize. To better understand the suitability of organic CT materials for electronic applications, we have devised an experimental technique that can directly assess electron-phonon coupling in a model organic CT material. Upon non-resonant interaction with an ultrafast laser pulse, we show that coherent excitation of Raman-active lattice vibrations of quinhydrone, a 1:1 co-crystal of the hydroquinone and p-benzoquinone, modulates the energies of electronic transitions probed by a white light pulse. Using a well-established theoretical framework of vibrational quantum beat spectra across the probe bandwidth, we quantitatively extract the parameters describing these electronic transitions to characterize electron-phonon coupling in this material. In conjunction with temperature-dependent resonance Raman measurements, we assess the hypothesis that several sharp transitions in the near-IR correspond to previously unknown excitonic states of this material. These results and their interpretation set the foundation for further elucidation of the one of the most important parameters in the application of organic charge-transfer materials to electronics and photonics.

Calcium measurements with electron probe X-ray and electron energy loss analysis.

PubMed

LeFurgey, A; Ingram, P

1990-03-01

This paper presents a broad survey of the rationale for electron probe X-ray microanalysis (EPXMA) and the various methods for obtaining qualitative and quantitative information on the distribution and amount of elements, particularly calcium, in cryopreserved cells and tissues. Essential in an introductory consideration of microanalysis in biological cryosections is the physical basis for the instrumentation, fundamentals of X-ray spectrometry, and various analytical modes such as static probing and X-ray imaging. Some common artifacts are beam damage and contamination. Inherent pitfalls of energy dispersive X-ray systems include Si escape peaks, doublets, background, and detector calibration shifts. Quantitative calcium analysis of thin cryosections is carried out in real time using a multiple least squares fitting program on filtered X-ray spectra and normalizing the calcium peak to a portion of the continuum. Recent work includes the development of an X-ray imaging system where quantitative data can be retrieved off-line. The minimum detectable concentration of calcium in biological cryosections is approximately 300 mumole kg dry weight with a spatial resolution of approximately 100 A. The application of electron energy loss (EELS) techniques to the detection of calcium offers the potential for greater sensitivity and spatial resolution in measurement and imaging. Determination of mass thickness with EELS can facilitate accurate calculation of wet weight concentrations from frozen hydrated and freeze-dried specimens. Calcium has multiple effects on cell metabolism, membrane transport and permeability and, thus, on overall cell physiology or pathophysiology. Cells can be rapidly frozen for EPXMA during basal or altered functional conditions to delineate the location and amount of calcium within cells and the changes in location and concentration of cations or anions accompanying calcium redistribution. Recent experiments in our laboratory document that EPXMA in

2-D energy analyzer for low energy electrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karkare, Siddharth, E-mail: ssk226@cornell.edu; Cultrera, Luca; Hwang, Yoon-Woo

2015-03-15

A 2-D electron energy analyzer is designed and constructed to measure the transverse and longitudinal energy distribution of low energy (<1 eV) electrons. The analyzer operates on the principle of adiabatic invariance and motion of low energy electrons in a strong longitudinal magnetic field. The operation of the analyzer is studied in detail and a design to optimize the energy resolution, signal to noise ratio, and physical size is presented. An energy resolution better than 6 meV has been demonstrated. Such an analyzer is a powerful tool to study the process of photoemission which limits the beam quality in modernmore » accelerators.« less

Microdosimetry of low-energy electrons.

PubMed

Liamsuwan, Thiansin; Emfietzoglou, Dimitris; Uehara, Shuzo; Nikjoo, Hooshang

2012-12-01

To investigate differences in energy depositions and microdosimetric parameters of low-energy electrons in liquid and gaseous water using Monte Carlo track structure simulations. KURBUC-liq (Kyushu University and Radiobiology Unit Code for liquid water) was used for simulating electron tracks in liquid water. The inelastic scattering cross sections of liquid water were obtained from the dielectric response model of Emfietzoglou et al. (Radiation Research 2005;164:202-211). Frequencies of energy deposited in nanometre-size cylindrical targets per unit absorbed dose and associated lineal energies were calculated for 100-5000 eV monoenergetic electrons and the electron spectrum of carbon K edge X-rays. The results for liquid water were compared with those for water vapour. Regardless of electron energy, there is a limit how much energy electron tracks can deposit in a target. Phase effects on the frequencies of energy depositions are largely visible for the targets with diameters and heights smaller than 30 nm. For the target of 2.3 nm by 2.3 nm (similar to dimension of DNA segments), the calculated frequency- and dose-mean lineal energies for liquid water are up to 40% smaller than those for water vapour. The corresponding difference is less than 12% for the targets with diameters ≥ 30 nm. Condensed-phase effects are non-negligible for microdosimetry of low-energy electrons for targets with sizes smaller than a few tens of nanometres, similar to dimensions of DNA molecular structures and nucleosomes.

Electron-lattice energy relaxation in laser-excited thin-film Au-insulator heterostructures studied by ultrafast MeV electron diffraction.

PubMed

Sokolowski-Tinten, K; Shen, X; Zheng, Q; Chase, T; Coffee, R; Jerman, M; Li, R K; Ligges, M; Makasyuk, I; Mo, M; Reid, A H; Rethfeld, B; Vecchione, T; Weathersby, S P; Dürr, H A; Wang, X J

2017-09-01

We apply time-resolved MeV electron diffraction to study the electron-lattice energy relaxation in thin film Au-insulator heterostructures. Through precise measurements of the transient Debye-Waller-factor, the mean-square atomic displacement is directly determined, which allows to quantitatively follow the temporal evolution of the lattice temperature after short pulse laser excitation. Data obtained over an extended range of laser fluences reveal an increased relaxation rate when the film thickness is reduced or the Au-film is capped with an additional insulator top-layer. This behavior is attributed to a cross-interfacial coupling of excited electrons in the Au film to phonons in the adjacent insulator layer(s). Analysis of the data using the two-temperature-model taking explicitly into account the additional energy loss at the interface(s) allows to deduce the relative strength of the two relaxation channels.

Direct Observation of Individual Charges and Their Dynamics on Graphene by Low-Energy Electron Holography.

PubMed

Latychevskaia, Tatiana; Wicki, Flavio; Longchamp, Jean-Nicolas; Escher, Conrad; Fink, Hans-Werner

2016-09-14

Visualizing individual charges confined to molecules and observing their dynamics with high spatial resolution is a challenge for advancing various fields in science, ranging from mesoscopic physics to electron transfer events in biological molecules. We show here that the high sensitivity of low-energy electrons to local electric fields can be employed to directly visualize individual charged adsorbates and to study their behavior in a quantitative way. This makes electron holography a unique probing tool for directly visualizing charge distributions with a sensitivity of a fraction of an elementary charge. Moreover, spatial resolution in the nanometer range and fast data acquisition inherent to lens-less low-energy electron holography allows for direct visual inspection of charge transfer processes.

Quantitative Near-field Microscopy of Heterogeneous and Correlated Electron Oxides

NASA Astrophysics Data System (ADS)

McLeod, Alexander Swinton

Scanning near-field optical microscopy (SNOM) is a novel scanning probe microscopy technique capable of circumventing the conventional diffraction limit of light, affording unparalleled optical resolution (down to 10 nanometers) even for radiation in the infrared and terahertz energy regimes, with light wavelengths exceeding 10 micrometers. However, although this technique has been developed and employed for more than a decade to a qualitatively impressive effect, researchers have lacked a practically quantitative grasp of its capabilities, and its application scope has so far remained restricted by implementations limited to ambient atmospheric conditions. The two-fold objective of this dissertation work has been to address both these shortcomings. The first half of the dissertation presents a realistic, semi-analytic, and benchmarked theoretical description of probe-sample near-field interactions that form the basis of SNOM. Owing its name to the efficient nano-focusing of light at a sharp metallic apex, the "lightning rod model" of probe-sample near-field interactions is mathematically developed from a flexible and realistic scattering formalism. Powerful and practical applications are demonstrated through the accurate prediction of spectroscopic near-field optical contrasts, as well as the "inversion" of these spectroscopic contrasts into a quantitative description of material optical properties. Thus enabled, this thesis work proceeds to present quantitative applications of infrared near-field spectroscopy to investigate nano-resolved chemical compositions in a diverse host of samples, including technologically relevant lithium ion battery materials, astrophysical planetary materials, and invaluable returned extraterrestrial samples. The second half of the dissertation presents the design, construction, and demonstration of a sophisticated low-temperature scanning near-field infrared microscope. This instrument operates in an ultra-high vacuum environment

Quantitative measurement of electron number in nanosecond and picosecond laser-induced air breakdown

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Yue; Sawyer, Jordan C.; Su, Liu

2016-05-07

Here we present quantitative measurements of total electron numbers in laser-induced air breakdown at pressures ranging from atmospheric to 40 bar{sub g} by 10 ns and 100 ps laser pulses. A quantifiable definition for the laser-induced breakdown threshold is identified by a sharp increase in the measurable total electron numbers via dielectric-calibrated coherent microwave scattering. For the 10 ns laser pulse, the threshold of laser-induced breakdown in atmospheric air is defined as the total electron number of ∼10{sup 6}. This breakdown threshold decreases with an increase of pressure and laser photon energy (shorter wavelength), which is consistent with the theory of initialmore » multiphoton ionization and subsequent avalanche processes. For the 100 ps laser pulse cases, a clear threshold is not present and only marginal pressure effects can be observed, which is due to the short pulse duration leading to stronger multiphoton ionization and minimal collisional avalanche ionization.« less

Electronic energy transfer: Localized operator partitioning of electronic energy in composite quantum systems

NASA Astrophysics Data System (ADS)

Khan, Yaser; Brumer, Paul

2012-11-01

A Hamiltonian based approach using spatially localized projection operators is introduced to give precise meaning to the chemically intuitive idea of the electronic energy on a quantum subsystem. This definition facilitates the study of electronic energy transfer in arbitrarily coupled quantum systems. In particular, the decomposition scheme can be applied to molecular components that are strongly interacting (with significant orbital overlap) as well as to isolated fragments. The result defines a consistent electronic energy at all internuclear distances, including the case of separated fragments, and reduces to the well-known Förster and Dexter results in their respective limits. Numerical calculations of coherent energy and charge transfer dynamics in simple model systems are presented and the effect of collisionally induced decoherence is examined.

Electronic energy level alignment at metal-molecule interfaces with a GW approach

NASA Astrophysics Data System (ADS)

Tamblyn, Isaac; Darancet, Pierre; Quek, Su Ying; Bonev, Stanimir A.; Neaton, Jeffrey B.

2011-11-01

Using density functional theory and many-body perturbation theory within a GW approximation, we calculate the electronic structure of a metal-molecule interface consisting of benzene diamine (BDA) adsorbed on Au(111). Through direct comparison with photoemission data, we show that a conventional G0W0 approach can underestimate the energy of the adsorbed molecular resonance relative to the Au Fermi level by up to 0.8 eV. The source of this discrepancy is twofold: a 0.7 eV underestimate of the gas phase ionization energy (IE), and a 0.2 eV overestimate of the Au work function. Refinements to self-energy calculations within the GW framework that account for deviations in both the Au work function and BDA gas-phase IE can result in an interfacial electronic level alignment in quantitative agreement with experiment.

Electron-lattice energy relaxation in laser-excited thin-film Au-insulator heterostructures studied by ultrafast MeV electron diffraction

PubMed Central

Sokolowski-Tinten, K.; Shen, X.; Zheng, Q.; Chase, T.; Coffee, R.; Jerman, M.; Li, R. K.; Ligges, M.; Makasyuk, I.; Mo, M.; Reid, A. H.; Rethfeld, B.; Vecchione, T.; Weathersby, S. P.; Dürr, H. A.; Wang, X. J.

2017-01-01

We apply time-resolved MeV electron diffraction to study the electron-lattice energy relaxation in thin film Au-insulator heterostructures. Through precise measurements of the transient Debye-Waller-factor, the mean-square atomic displacement is directly determined, which allows to quantitatively follow the temporal evolution of the lattice temperature after short pulse laser excitation. Data obtained over an extended range of laser fluences reveal an increased relaxation rate when the film thickness is reduced or the Au-film is capped with an additional insulator top-layer. This behavior is attributed to a cross-interfacial coupling of excited electrons in the Au film to phonons in the adjacent insulator layer(s). Analysis of the data using the two-temperature-model taking explicitly into account the additional energy loss at the interface(s) allows to deduce the relative strength of the two relaxation channels. PMID:28795080

Runaway Signatures in the Transport Description of Solar Wind Electrons: A New Quantitative Steady Electron Runaway Model (SERM)

NASA Astrophysics Data System (ADS)

Scudder, J. D.; Salem, C. S.

2016-12-01

A new model for solar wind electrons provides an explanation for the origin of the non-thermal core-halo-strahl-superhalo VDF ubiquitously observed in the solar wind. Such kurtotic VDF's should be as common as the gradient induced occurrence of finite parallel electric fields that enforce quasi-neutrality in astrophysical plasmas. The velocity space separatrix of coulomb runaway predicts the observed scaling of the break point energy at 1AU of the electron VDF between thermal and suprathermal components and agrees well with the tabulations of its variation with radius. SERM quantitatively reproduces: 14 year IMP archives of the fraction of supra thermal electrons and the observed variation of the supra thermal density with local (nearly asymptotic) solar wind speed; the observed inverse correlation between halo density fraction and Th/Tc; and the reported, but theoretically unusual relative slippage of the core and halo that supports the heat flux. Requirements for quasi-neutrality (in the presence of runaways) lead to a quantitative non-local specification of the required supra thermal density fraction and the lowest even Legendre order approximate VDF that is symmetric, but kurtotic in the proton rest frame. The Stokes drift of the thermals suggested by runaway physics requires a counter drift of the non-locally returning suprathermals which determine the observed heat flux and thermal force contributions and the lowest order odd Legendre dependence of the VDF. The strahl is recovered as an extreme part of the non-local suprathermals. "Direct'' runaways caused by the parallel electric field are identified as an omnipresent source for the observed sunward portion of the non-thermal VDF. The source of the super halo electrons is suggested to be mirrored runaways produced at the base of the corona with subsequent near isotropization in the interplanetary medium.

Electronic Excitation of Furan by Low Energy Electrons

NASA Astrophysics Data System (ADS)

Hargreaves, Leigh R.; Khakoo, Murtadha A.; Lopes, Maria Cristina A.; da Costa, Romarly; Bettega, Marcio H. F.; Lima, Marco A. P.

2011-10-01

We present absolute differential cross section (DCS) measurements and calculations of electron impact excitation of the lowest lying triplet 3B2 and 3A1 electronic states of furan. The incident electron energy range of the present study was 5-15eV. The experimental data were normalized to the elastic DCS data of. The cross sections were determined by unfolding electron energy loss spectra, using an open source data analysis package and the spectroscopic assignments of. The calculations employ a Multichannel Schwinger method with a 9-state closed coupling CI configuration including polarized pseudo-potentials. The preliminary theoretical results show reasonable agreement with experiment below 10eV, but differ at higher energies. Funded by the US NSF and the Brazilian funding agencies CNPq, CAPES and FAPESP.

Quantitative molecular orbital energies within a G0W0 approximation

NASA Astrophysics Data System (ADS)

Sharifzadeh, S.; Tamblyn, I.; Doak, P.; Darancet, P. T.; Neaton, J. B.

2012-09-01

Using many-body perturbation theory within a G 0 W 0 approximation, with a plane wave basis set and using a starting point based on density functional theory within the generalized gradient approximation, we explore routes for computing the ionization potential (IP), electron affinity (EA), and fundamental gap of three gas-phase molecules — benzene, thiophene, and (1,4) diamino-benzene — and compare with experiments. We examine the dependence of the IP and fundamental gap on the number of unoccupied states used to represent the dielectric function and the self energy, as well as the dielectric function plane-wave cutoff. We find that with an effective completion strategy for approximating the unoccupied subspace, and a well converged dielectric function kinetic energy cutoff, the computed IPs and EAs are in excellent quantitative agreement with available experiment (within 0.2 eV), indicating that a one-shot G 0 W 0 approach can be very accurate for calculating addition/removal energies of small organic molecules.

Low energy electron catalyst: the electronic origin of catalytic strategies.

PubMed

Davis, Daly; Sajeev, Y

2016-10-12

Using a low energy electron (LEE) as a catalyst, the electronic origin of the catalytic strategies corresponding to substrate selectivity, reaction specificity and reaction rate enhancement is investigated for a reversible unimolecular elementary reaction. An electronic energy complementarity between the catalyst and the substrate molecule is the origin of substrate selectivity and reaction specificity. The electronic energy complementarity is induced by tuning the electronic energy of the catalyst. The energy complementarity maximizes the binding forces between the catalyst and the molecule. Consequently, a new electronically metastable high-energy reactant state and a corresponding new low barrier reaction path are resonantly created for a specific reaction of the substrate through the formation of a catalyst-substrate transient adduct. The LEE catalysis also reveals a fundamental structure-energy correspondence in the formation of the catalyst-substrate transient adduct. Since the energy complementarities corresponding to the substrate molecules of the forward and the backward steps of the reversible reactions are not the same due to their structural differences, the LEE catalyst exhibits a unique one-way catalytic strategy, i.e., the LEE catalyst favors the reversible reaction more effectively in one direction. A characteristic stronger binding of the catalyst to the transition state of the reaction than in the initial reactant state and the final product state is the molecular origin of barrier lowering.

Energy Dispersive Spectrometry and Quantitative Analysis Short Course. Introduction to X-ray Energy Dispersive Spectrometry and Quantitative Analysis

NASA Technical Reports Server (NTRS)

Carpenter, Paul; Curreri, Peter A. (Technical Monitor)

2002-01-01

This course will cover practical applications of the energy-dispersive spectrometer (EDS) to x-ray microanalysis. Topics covered will include detector technology, advances in pulse processing, resolution and performance monitoring, detector modeling, peak deconvolution and fitting, qualitative and quantitative analysis, compositional mapping, and standards. An emphasis will be placed on use of the EDS for quantitative analysis, with discussion of typical problems encountered in the analysis of a wide range of materials and sample geometries.

Electronic energy density in chemical reaction systems

NASA Astrophysics Data System (ADS)

Tachibana, Akitomo

2001-08-01

The energy of chemical reaction is visualized in real space using the electronic energy density nE(r⃗) associated with the electron density n(r⃗). The electronic energy density nE(r⃗) is decomposed into the kinetic energy density nT(r⃗), the external potential energy density nV(r⃗), and the interelectron potential energy density nW(r⃗). Using the electronic energy density nE(r⃗) we can pick up any point in a chemical reaction system and find how the electronic energy E is assigned to the selected point. We can then integrate the electronic energy density nE(r⃗) in any region R surrounding the point and find out the regional electronic energy ER to the global E. The kinetic energy density nT(r⃗) is used to identify the intrinsic shape of the reactants, the electronic transition state, and the reaction products along the course of the chemical reaction coordinate. The intrinsic shape is identified with the electronic interface S that discriminates the region RD of the electronic drop from the region RA of the electronic atmosphere in the density distribution of the electron gas. If the R spans the whole space, then the integral gives the total E. The regional electronic energy ER in thermodynamic ensemble is realized in electrochemistry as the intrinsic Volta electric potential φR and the intrinsic Herring-Nichols work function ΦR. We have picked up first a hydrogen-like atom for which we have analytical exact expressions of the relativistic kinetic energy density nTM(r⃗) and its nonrelativistic version nT(r⃗). These expressions are valid for any excited bound states as well as the ground state. Second, we have selected the following five reaction systems and show the figures of the nT(r⃗) as well as the other energy densities along the intrinsic reaction coordinates: a protonation reaction to He, addition reactions of HF to C2H4 and C2H2, hydrogen abstraction reactions of NH3+ from HF and NH3. Valence electrons possess their unique

Quantitative Electron Probe Microanalysis: State of the Art

NASA Technical Reports Server (NTRS)

Carpernter, P. K.

2005-01-01

Quantitative electron-probe microanalysis (EPMA) has improved due to better instrument design and X-ray correction methods. Design improvement of the electron column and X-ray spectrometer has resulted in measurement precision that exceeds analytical accuracy. Wavelength-dispersive spectrometer (WDS) have layered-dispersive diffraction crystals with improved light-element sensitivity. Newer energy-dispersive spectrometers (EDS) have Si-drift detector elements, thin window designs, and digital processing electronics with X-ray throughput approaching that of WDS Systems. Using these systems, digital X-ray mapping coupled with spectrum imaging is a powerful compositional mapping tool. Improvements in analytical accuracy are due to better X-ray correction algorithms, mass absorption coefficient data sets,and analysis method for complex geometries. ZAF algorithms have ban superceded by Phi(pz) algorithms that better model the depth distribution of primary X-ray production. Complex thin film and particle geometries are treated using Phi(pz) algorithms, end results agree well with Monte Carlo simulations. For geological materials, X-ray absorption dominates the corretions end depends on the accuracy of mass absorption coefficient (MAC) data sets. However, few MACs have been experimentally measured, and the use of fitted coefficients continues due to general success of the analytical technique. A polynomial formulation of the Bence-Albec alpha-factor technique, calibrated using Phi(pz) algorithms, is used to critically evaluate accuracy issues and can be also be used for high 2% relative and is limited by measurement precision for ideal cases, but for many elements the analytical accuracy is unproven. The EPMA technique has improved to the point where it is frequently used instead of the petrogaphic microscope for reconnaissance work. Examples of stagnant research areas are: WDS detector design characterization of calibration standards, and the need for more complete

Direct determination of energy level alignment and charge transport at metal-Alq3 interfaces via ballistic-electron-emission spectroscopy.

PubMed

Jiang, J S; Pearson, J E; Bader, S D

2011-04-15

Using ballistic-electron-emission spectroscopy (BEES), we directly determined the energy barrier for electron injection at clean interfaces of Alq(3) with Al and Fe to be 2.1 and 2.2 eV, respectively. We quantitatively modeled the sub-barrier BEES spectra with an accumulated space charge layer, and found that the transport of nonballistic electrons is consistent with random hopping over the injection barrier.

Quantitative determination of low-Z elements in single atmospheric particles on boron substrates by automated scanning electron microscopy-energy-dispersive X-ray spectrometry.

PubMed

Choël, Marie; Deboudt, Karine; Osán, János; Flament, Pascal; Van Grieken, René

2005-09-01

Atmospheric aerosols consist of a complex heterogeneous mixture of particles. Single-particle analysis techniques are known to provide unique information on the size-resolved chemical composition of aerosols. A scanning electron microscope (SEM) combined with a thin-window energy-dispersive X-ray (EDX) detector enables the morphological and elemental analysis of single particles down to 0.1 microm with a detection limit of 1-10 wt %, low-Z elements included. To obtain data statistically representative of the air masses sampled, a computer-controlled procedure can be implemented in order to run hundreds of single-particle analyses (typically 1000-2000) automatically in a relatively short period of time (generally 4-8 h, depending on the setup and on the particle loading). However, automated particle analysis by SEM-EDX raises two practical challenges: the accuracy of the particle recognition and the reliability of the quantitative analysis, especially for micrometer-sized particles with low atomic number contents. Since low-Z analysis is hampered by the use of traditional polycarbonate membranes, an alternate choice of substrate is a prerequisite. In this work, boron is being studied as a promising material for particle microanalysis. As EDX is generally said to probe a volume of approximately 1 microm3, geometry effects arise from the finite size of microparticles. These particle geometry effects must be corrected by means of a robust concentration calculation procedure. Conventional quantitative methods developed for bulk samples generate elemental concentrations considerably in error when applied to microparticles. A new methodology for particle microanalysis, combining the use of boron as the substrate material and a reverse Monte Carlo quantitative program, was tested on standard particles ranging from 0.25 to 10 microm. We demonstrate that the quantitative determination of low-Z elements in microparticles is achievable and that highly accurate results can be

Development of a secondary electron energy analyzer for a transmission electron microscope.

PubMed

Magara, Hideyuki; Tomita, Takeshi; Kondo, Yukihito; Sato, Takafumi; Akase, Zentaro; Shindo, Daisuke

2018-04-01

A secondary electron (SE) energy analyzer was developed for a transmission electron microscope. The analyzer comprises a microchannel plate (MCP) for detecting electrons, a coil for collecting SEs emitted from the specimen, a tube for reducing the number of backscattered electrons incident on the MCP, and a retarding mesh for selecting the energy of SEs incident on the MCP. The detection of the SEs associated with charging phenomena around a charged specimen was attempted by performing electron holography and SE spectroscopy using the energy analyzer. The results suggest that it is possible to obtain the energy spectra of SEs using the analyzer and the charging states of a specimen by electron holography simultaneously.

Ultrafast Electron Dynamics in Solar Energy Conversion.

PubMed

Ponseca, Carlito S; Chábera, Pavel; Uhlig, Jens; Persson, Petter; Sundström, Villy

2017-08-23

Electrons are the workhorses of solar energy conversion. Conversion of the energy of light to electricity in photovoltaics, or to energy-rich molecules (solar fuel) through photocatalytic processes, invariably starts with photoinduced generation of energy-rich electrons. The harvesting of these electrons in practical devices rests on a series of electron transfer processes whose dynamics and efficiencies determine the function of materials and devices. To capture the energy of a photogenerated electron-hole pair in a solar cell material, charges of opposite sign have to be separated against electrostatic attractions, prevented from recombining and being transported through the active material to electrodes where they can be extracted. In photocatalytic solar fuel production, these electron processes are coupled to chemical reactions leading to storage of the energy of light in chemical bonds. With the focus on the ultrafast time scale, we here discuss the light-induced electron processes underlying the function of several molecular and hybrid materials currently under development for solar energy applications in dye or quantum dot-sensitized solar cells, polymer-fullerene polymer solar cells, organometal halide perovskite solar cells, and finally some photocatalytic systems.

Demonstration of transmission high energy electron microscopy

DOE PAGES

Merrill, F. E.; Goett, J.; Gibbs, J. W.; ...

2018-04-06

High energy electrons have been used to investigate an extension of transmission electron microscopy. This technique, transmission high energy electron microscopy (THEEM), provides two additional capabilities to electron microscopy. First, high energy electrons are more penetrating than low energy electrons, and thus, they are able to image through thicker samples. Second, the accelerating mode of a radio-frequency linear accelerator provides fast exposures, down to 1 ps, which are ideal for flash radiography, making THEEM well suited to study the evolution of fast material processes under dynamic conditions. Lastly, initial investigations with static objects and during material processing have been performedmore » to investigate the capabilities of this technique.« less

Absolute Scale Quantitative Off-Axis Electron Holography at Atomic Resolution

NASA Astrophysics Data System (ADS)

Winkler, Florian; Barthel, Juri; Tavabi, Amir H.; Borghardt, Sven; Kardynal, Beata E.; Dunin-Borkowski, Rafal E.

2018-04-01

An absolute scale match between experiment and simulation in atomic-resolution off-axis electron holography is demonstrated, with unknown experimental parameters determined directly from the recorded electron wave function using an automated numerical algorithm. We show that the local thickness and tilt of a pristine thin WSe2 flake can be measured uniquely, whereas some electron optical aberrations cannot be determined unambiguously for a periodic object. The ability to determine local specimen and imaging parameters directly from electron wave functions is of great importance for quantitative studies of electrostatic potentials in nanoscale materials, in particular when performing in situ experiments and considering that aberrations change over time.

Diffraction of electrons at intermediate energies

NASA Astrophysics Data System (ADS)

Ascolani, H.; Barrachina, R. O.; Guraya, M. M.; Zampieri, G.

1992-08-01

We present a theory of the elastic scattering of electrons from crystalline surfaces that contains both low-energy-electron-diffraction (LEED) effects at low energies and x-ray-photoelectron- and Auger-electron-diffraction (XPD/AED) effects at intermediate energies. The theory is based on a cluster-type approach to the scattering problem and includes temperature effects. The transition from one regime to the other may be explained as follows: At low energies all the scattered waves add coherently, and the intensity is dominated by LEED effects. At intermediate energies the thermal vibration of the atoms destroys the long-range coherency responsible for the LEED peaks, but affects little the interference of those waves that share parts of their paths inside the solid. Thus, the interference of these waves comes to dominate the intensity, giving rise to structures similar to those observed in XPD/AED experiments. We perform a calculation of the elastic reflection of electrons from Cu(001) that is in good agreement with the experiment in the range 200-1500 eV. At low energies the intensity is dominated by LEED peaks; at 400 eV LEED peaks and XPD/AED structures coexist; and above this energy the intensity is dominated by the latter. We analyze the contributions to the intensity at intermediate energies of the interferences in the incoming and outgoing parts of the electron path.

A Method to Improve Electron Density Measurement of Cone-Beam CT Using Dual Energy Technique

PubMed Central

Men, Kuo; Dai, Jian-Rong; Li, Ming-Hui; Chen, Xin-Yuan; Zhang, Ke; Tian, Yuan; Huang, Peng; Xu, Ying-Jie

2015-01-01

Purpose. To develop a dual energy imaging method to improve the accuracy of electron density measurement with a cone-beam CT (CBCT) device. Materials and Methods. The imaging system is the XVI CBCT system on Elekta Synergy linac. Projection data were acquired with the high and low energy X-ray, respectively, to set up a basis material decomposition model. Virtual phantom simulation and phantoms experiments were carried out for quantitative evaluation of the method. Phantoms were also scanned twice with the high and low energy X-ray, respectively. The data were decomposed into projections of the two basis material coefficients according to the model set up earlier. The two sets of decomposed projections were used to reconstruct CBCT images of the basis material coefficients. Then, the images of electron densities were calculated with these CBCT images. Results. The difference between the calculated and theoretical values was within 2% and the correlation coefficient of them was about 1.0. The dual energy imaging method obtained more accurate electron density values and reduced the beam hardening artifacts obviously. Conclusion. A novel dual energy CBCT imaging method to calculate the electron densities was developed. It can acquire more accurate values and provide a platform potentially for dose calculation. PMID:26346510

Investigating fold structures of 2D materials by quantitative transmission electron microscopy.

PubMed

Wang, Zhiwei; Zhang, Zengming; Liu, Wei; Wang, Zhong Lin

2017-04-01

We report an approach developed for deriving 3D structural information of 2D membrane folds based on the recently-established quantitative transmission electron microscopy (TEM) in combination with density functional theory (DFT) calculations. Systematic multislice simulations reveal that the membrane folding leads to sufficiently strong electron scattering which enables a precise determination of bending radius. The image contrast depends also on the folding angles of 2D materials due to the variation of projection potentials, which however exerts much smaller effect compared with the bending radii. DFT calculations show that folded edges are typically characteristic of (fractional) nanotubes with the same curvature retained after energy optimization. Owing to the exclusion of Stobbs factor issue, numerical simulations were directly used in comparison with the experimental measurements on an absolute contrast scale, which results in a successful determination of bending radius of folded monolayer MoS 2 films. The method should be applicable to characterizing all 2D membranes with 3D folding features. Copyright © 2017 Elsevier Ltd. All rights reserved.

Transmission effects in unfolding electronic-vibrational electron-molecule energy-loss spectra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Shiyang; Khakoo, Murtadha A.; Johnson, Paul V.

2006-03-15

The results of an investigation concerning the sensitivity of conventional unfolding methods applied to electronic-vibrational electron-energy-loss spectra to the transmission efficiency of electron spectrometers are presented. This investigation was made in an effort to understand differences in the differential cross sections for excitation of low-lying electronic states determined experimentally by various groups using electronic-vibrational energy-loss spectra of N{sub 2}. In these experiments, very similar spectral unfolding methods were used, which relied on similar Franck-Condon factors. However, the overall analyses of the electron scattering spectra (by the individual groups) resulted in large differences among the differential cross sections determined from thesemore » energy-loss spectra. The transmission response of the experimental apparatus to different-energy scattered electrons has often been discussed as a key factor that caused these disagreements. The present investigation shows in contrast that the effect of transmission is smaller than that required to independently explain such differences, implying that other systematic effects are responsible for the existing differences between measurements.« less

Accurate Virus Quantitation Using a Scanning Transmission Electron Microscopy (STEM) Detector in a Scanning Electron Microscope

DTIC Science & Technology

2017-06-29

Accurate Virus Quantitation Using a Scanning Transmission Electron Microscopy (STEM) Detector in a Scanning Electron Microscope Candace D Blancett1...L Norris2, Cynthia A Rossi4 , Pamela J Glass3, Mei G Sun1,* 1 Pathology Division, United States Army Medical Research Institute of Infectious...Diseases (USAMRIID), 1425 Porter Street, Fort Detrick, Maryland, 21702 2Biostatistics Division, United States Army Medical Research Institute of

SU-E-T-635: Quantitative Study On Beam Flatness Variation with Beam Energy Change

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, J S; Eldib, A; Ma, C

2014-06-15

Purpose: Beam flatness check has been proposed for beam energy check for photon beams with flattering filters. In this work, beam flatness change with beam energy was investigated quantitatively using the Monte Carlo method and its significance was compared with depth dose curve change. Methods: Monte Carlo simulations for a linear accelerator with flattering filter were performed with different initial electron energies for photon beams of 6MV and 10MV. Dose calculations in a water phantom were then perform with the phase space files obtained from the simulations. The beam flatness was calculated based on the dose profile at 10 cmmore » depth for all the beams with different initial electron energies. The percentage depth dose (PDD) curves were also analyzed. The dose at 10cm depth (D10) and the ratio of the dose at 10cm and 20cm depth (D10/D20) and their change with the beam energy were calculated and compared with the beam flatness variation. Results: It was found that the beam flatness variation with beam energy change was more significant than the change of D10 and the ratio between D10 and D20 for both 6MV and 10MV beams. Half MeV difference on the initial electron beam energy brought in at least 20% variation on the beam flatness but only half percent change on the ratio of D10 and D20. The change of D10 or D20 alone is even less significant. Conclusion: The beam energy impact on PDD is less significant than that on the beam flatness. If the PDD is used for checking the beam energy, uncertainties of the measurement could possibly disguise its change. Beam flatness changes more significantly with beam energy and therefore it can be used for monitoring the energy change for photon beams with flattering filters. However, other factors which may affect the beam flatness should be watched as well.« less

Quantitative structure-retention relationship studies using immobilized artificial membrane chromatography I: amended linear solvation energy relationships with the introduction of a molecular electronic factor.

PubMed

Li, Jie; Sun, Jin; Cui, Shengmiao; He, Zhonggui

2006-11-03

Linear solvation energy relationships (LSERs) amended by the introduction of a molecular electronic factor were employed to establish quantitative structure-retention relationships using immobilized artificial membrane (IAM) chromatography, in particular ionizable solutes. The chromatographic indices, log k(IAM), were determined by HPLC on an IAM.PC.DD2 column for 53 structurally diverse compounds, including neutral, acidic and basic compounds. Unlike neutral compounds, the IAM chromatographic retention of ionizable compounds was affected by their molecular charge state. When the mean net charge per molecule (delta) was introduced into the amended LSER as the sixth variable, the LSER regression coefficient was significantly improved for the test set including ionizable solutes. The delta coefficients of acidic and basic compounds were quite different indicating that the molecular electronic factor had a markedly different impact on the retention of acidic and basic compounds on IAM column. Ionization of acidic compounds containing a carboxylic group tended to impair their retention on IAM, while the ionization of basic compounds did not have such a marked effect. In addition, the extra-interaction with the polar head of phospholipids might cause a certain change in the retention of basic compounds. A comparison of calculated and experimental retention indices suggested that the semi-empirical LSER amended by the addition of a molecular electronic factor was able to reproduce adequately the experimental retention factors of the structurally diverse solutes investigated.

Direct determination of energy level alignment and charge transport at metal/Alq{sub 3} interfaces via ballistic-electron-emission spectroscopy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, J. S.; Pearson, J. E.; Bader, S. D.

2011-04-15

Using ballistic-electron-emission spectroscopy (BEES), we directly determined the energy barrier for electron injection at clean interfaces of Alq{sub 3} with Al and Fe to be 2.1 and 2.2 eV, respectively. We quantitatively modeled the sub-barrier BEES spectra with an accumulated space charge layer, and found that the transport of nonballistic electrons is consistent with random hopping over the injection barrier.

Energy spectrum of cosmic-ray electrons at TeV energies.

PubMed

Aharonian, F; Akhperjanian, A G; Barres de Almeida, U; Bazer-Bachi, A R; Becherini, Y; Behera, B; Benbow, W; Bernlöhr, K; Boisson, C; Bochow, A; Borrel, V; Braun, I; Brion, E; Brucker, J; Brun, P; Brucker, R; Bulik, T; Büsching, I; Boutelier, T; Carrigan, S; Chadwick, P M; Charbonnier, A; Chaves, R C G; Cheesebrough, A; Chounet, L M; Clapson, A C; Coignet, G; Costamante, L; Dalton, M; Degrange, B; Deil, C; Dickinson, H J; Djannati-Ataï, A; Domainko, W; Drury, L O'C; Dubois, F; Dubus, G; Dyks, J; Dyrda, M; Egberts, K; Emmanoulopoulos, D; Espigat, P; Farnier, C; Feinstein, F; Fiasson, A; Fontaine, G; Füsling, M; Gabici, S; Gallant, Y A; Gérard, L; Giebels, B; Glicenstein, J F; Glück, B; Goret, P; Hadjichristidis, C; Hauser, D; Hauser, M; Heinz, S; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hoffmann, A; Hofmann, W; Holleran, M; Hoppe, S; Horns, D; Jacholkowska, A; de Jager, O C; Jung, I; Katarzyński, K; Kaufmann, S; Kendziorra, E; Kerschhaggl, M; Khangulyan, D; Khélifi, B; Keogh, D; Komin, Nu; Kosack, K; Lamanna, G; Lenain, J P; Lohse, T; Marandon, V; Martin, J M; Martineau-Huynh, O; Marcowith, A; Maurin, D; McComb, T J L; Medina, C; Moderski, R; Moulin, E; Naumann-Godo, M; de Naurois, M; Nedbal, D; Nekrassov, D; Niemiec, J; Nolan, S J; Ohm, S; Olive, J F; de Oña Wilhelmi, E; Orford, K J; Osborne, J L; Ostrowski, M; Panter, M; Pedaletti, G; Pelletier, G; Petrucci, P O; Pita, S; Pühlhofer, G; Punch, M; Quirrenbach, A; Raubenheimer, B C; Raue, M; Rayner, S M; Renaud, M; Rieger, F; Ripken, J; Rob, L; Rosier-Lees, S; Rowell, G; Rudak, B; Rulten, C B; Ruppel, J; Sahakian, V; Santangelo, A; Schlickeiser, R; Schöck, F M; Schröder, R; Schwanke, U; Schwarzburg, S; Schwemmer, S; Shalchi, A; Skilton, J L; Sol, H; Spangler, D; Stawarz, Ł; Steenkamp, R; Stegmann, C; Superina, G; Tam, P H; Tavernet, J P; Terrier, R; Tibolla, O; van Eldik, C; Vasileiadis, G; Venter, C; Vialle, J P; Vincent, P; Vivier, M; Völk, H J; Volpe, F; Wagner, S J; Ward, M; Zdziarski, A A; Zech, A

2008-12-31

The very large collection area of ground-based gamma-ray telescopes gives them a substantial advantage over balloon or satellite based instruments in the detection of very-high-energy (>600 GeV) cosmic-ray electrons. Here we present the electron spectrum derived from data taken with the High Energy Stereoscopic System (H.E.S.S.) of imaging atmospheric Cherenkov telescopes. In this measurement, the first of this type, we are able to extend the measurement of the electron spectrum beyond the range accessible to direct measurements. We find evidence for a substantial steepening in the energy spectrum above 600 GeV compared to lower energies.

Thermoluminescent dosimetry in electron beams: energy dependence.

PubMed

Robar, V; Zankowski, C; Olivares Pla, M; Podgorsak, E B

1996-05-01

The response of thermoluminescent dosimeters to electron irradiations depends on the radiation dose, mean electron energy at the position of the dosimeter in phantom, and the size of the dosimeter. In this paper the semi-empirical expression proposed by Holt et al. [Phys. Med. Biol. 20, 559-570 (1975)] is combined with the calculated electron dose fraction to determine the thermoluminescent dosimetry (TLD) response as a function of the mean electron energy and the dosimeter size. The electron and photon dose fractions, defined as the relative contributions of electrons and bremsstrahlung photons to the total dose for a clinical electron beam, are calculated with Monte Carlo techniques using EGS4. Agreement between the calculated and measured TLD response is very good. We show that the considerable reduction in TLD response per unit dose at low electron energies, i.e., at large depths in phantom, is offset by an ever-increasing relative contribution of bremsstrahlung photons to the total dose of clinical electron beams. This renders the TLD sufficiently reliable for dose measurements over the entire electron depth dose distribution despite the dependence of the TLD response on electron beam energy.

SURVIVAL DEPTH OF ORGANICS IN ICES UNDER LOW-ENERGY ELECTRON RADIATION ({<=}2 keV)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barnett, Irene Li; Lignell, Antti; Gudipati, Murthy S., E-mail: gudipati@jpl.nasa.gov

2012-03-01

Icy surfaces in our solar system are continually modified and sputtered with electrons, ions, and photons from solar wind, cosmic rays, and local magnetospheres in the cases of Jovian and Saturnian satellites. In addition to their prevalence, electrons specifically are expected to be a principal radiolytic agent on these satellites. Among energetic particles (electrons and ions), electrons penetrate by far the deepest into the ice and could cause damage to organic material of possible prebiotic and even biological importance. To determine if organic matter could survive and be detected through remote sensing or in situ explorations on these surfaces, suchmore » as water ice-rich Europa, it is important to obtain accurate data quantifying electron-induced chemistry and damage depths of organics at varying incident electron energies. Experiments reported here address the quantification issue at lower electron energies (100 eV-2 keV) through rigorous laboratory data analysis obtained using a novel methodology. A polycyclic aromatic hydrocarbon molecule, pyrene, embedded in amorphous water ice films of controlled thicknesses served as an organic probe. UV-VIS spectroscopic measurements enabled quantitative assessment of organic matter survival depths in water ice. Eight ices of various thicknesses were studied to determine damage depths more accurately. The electron damage depths were found to be linear, approximately 110 nm keV{sup -1}, in the tested range which is noticeably higher than predictions by Monte Carlo simulations by up to 100%. We conclude that computational simulations underestimate electron damage depths in the energy region {<=}2 keV. If this trend holds at higher electron energies as well, present models utilizing radiation-induced organic chemistry in icy solar system bodies need to be revisited. For interstellar ices of a few micron thicknesses, we conclude that low-energy electrons generated through photoionization processes in the interstellar

Dynamic molecular structure retrieval from low-energy laser-induced electron diffraction spectra

NASA Astrophysics Data System (ADS)

Vu, Dinh-Duy T.; Phan, Ngoc-Loan T.; Hoang, Van-Hung; Le, Van-Hoang

2017-12-01

A recently developed quantitative rescattering theory showed that a laser-free elastic cross section can be separated from laser-induced electron diffraction (LIED) spectra. Based upon this idea, Blaga et al investigated the possibility of reconstructing molecular structure from LIED spectra (2012 Nature 483 7388). In the above study, an independent atoms model (IAM) was used to interpret high-energy electron-molecule collisions induced by a mid-infrared laser. Our research aims to extend the application range of this structural retrieval method to low-energy spectra induced by more common near-infrared laser sources. The IAM is insufficient in this case, so we switch to a more comprehensive model—the multiple scattering (MS) theory. From the original version concerning only neutral targets, we upgrade the model so that it is compatible with electron-ion collisions at low energy. With available LIED experiment data of CO2 and O2, the upgraded MS is shown to be greatly effective as a tool for molecular imaging from spectra induced by a near-infrared laser. The captured image is at about 2 fs after the ionization, shorter than the period 4-6 fs by using the mid-infrared laser in Blaga’s experiment.

Femtosecond MeV Electron Energy-Loss Spectroscopy

NASA Astrophysics Data System (ADS)

Li, R. K.; Wang, X. J.

2017-11-01

Pump-probe electron energy-loss spectroscopy (EELS) with femtosecond temporal resolution will be a transformative research tool for studying nonequilibrium chemistry and electronic dynamics of matter. In this paper, we propose a concept of femtosecond EELS utilizing mega-electron-volt electron beams from a radio-frequency (rf) photocathode source. The high acceleration gradient and high beam energy of the rf gun are critical to the generation of 10-fs electron beams, which enables an improvement of the temporal resolution by more than 1 order of magnitude beyond the state of the art. In our proposal, the "reference-beam technique" relaxes the energy stability requirement of the rf power source by roughly 2 orders of magnitude. The requirements for the electron-beam quality, photocathode, spectrometer, and detector are also discussed. Supported by particle-tracking simulations, we demonstrate the feasibility of achieving sub-electron-volt energy resolution and approximately 10-fs temporal resolution with existing or near-future hardware performance.

Quantitative variability of renewable energy resources in Norway

NASA Astrophysics Data System (ADS)

Christakos, Konstantinos; Varlas, George; Cheliotis, Ioannis; Aalstad, Kristoffer; Papadopoulos, Anastasios; Katsafados, Petros; Steeneveld, Gert-Jan

2017-04-01

Based on European Union (EU) targets for 2030, the share of renewable energy (RE) consumption should be increased at 27%. RE resources such as hydropower, wind, wave power and solar power are strongly depending on the chaotic behavior of the weather conditions and climate. Due to this dependency, the prediction of the spatiotemporal variability of the RE resources is more crucial factor than in other energy resources (i.e. carbon based energy). The fluctuation of the RE resources can affect the development of the RE technologies, the energy grid, supply and prices. This study investigates the variability of the potential RE resources in Norway. More specifically, hydropower, wind, wave, and solar power are quantitatively analyzed and correlated with respect to various spatial and temporal scales. In order to analyze the diversities and their interrelationships, reanalysis and observational data of wind, precipitation, wave, and solar radiation are used for a quantitative assessment. The results indicate a high variability of marine RE resources in the North Sea and the Norwegian Sea.

The Energy Spectrum of Solar Energetic Electrons

NASA Astrophysics Data System (ADS)

Wang, L.; Yang, L.; Krucker, S.; Wimmer-Schweingruber, R. F.; Bale, S. D.

2015-12-01

Here we present a statistical survey of the energy spectrum of solar energetic electron events (SEEs) observed by the WIND 3DP instrument from 1995 though 2014. For SEEs with the minimum energy below 10 keV and the maximum energy above 100 keV, ~85% (~2%) have a double-power-law energy spectrum with a steepening (hardening) above the break energy, while ~13% have a single-power-law energy spectrum at all energies. The average spectral index is ~2.4 below the energy break and is ~4.0 above the energy break. For SEEs detected only at energies <10 keV (>20 keV), they generally show a single-power-law spectrum with the average index of ~3.0 (~3.3). The spectrum of SEEs detected only below 10 keV appears to get harder with increasing solar activity, but the spectrum of SEEs with higher-energy electrons shows no clear correlation with solar activity. We will also investigate whether the observed energy spectrum of SEEs at 1 AU mainly reflects the electron acceleration at the Sun or the electron transport in the interplanetary medium.

Digital direct electron imaging of energy-filtered electron backscatter diffraction patterns

NASA Astrophysics Data System (ADS)

Vespucci, S.; Winkelmann, A.; Naresh-Kumar, G.; Mingard, K. P.; Maneuski, D.; Edwards, P. R.; Day, A. P.; O'Shea, V.; Trager-Cowan, C.

2015-11-01

Electron backscatter diffraction is a scanning electron microscopy technique used to obtain crystallographic information on materials. It allows the nondestructive mapping of crystal structure, texture, and strain with a lateral and depth resolution on the order of tens of nanometers. Electron backscatter diffraction patterns (EBSPs) are presently acquired using a detector comprising a scintillator coupled to a digital camera, and the crystallographic information obtainable is limited by the conversion of electrons to photons and then back to electrons again. In this article we will report the direct acquisition of energy-filtered EBSPs using a digital complementary metal-oxide-semiconductor hybrid pixel detector, Timepix. We show results from a range of samples with different mass and density, namely diamond, silicon, and GaN. Direct electron detection allows the acquisition of EBSPs at lower (≤5 keV) electron beam energies. This results in a reduction in the depth and lateral extension of the volume of the specimen contributing to the pattern and will lead to a significant improvement in lateral and depth resolution. Direct electron detection together with energy filtering (electrons having energy below a specific value are excluded) also leads to an improvement in spatial resolution but in addition provides an unprecedented increase in the detail in the acquired EBSPs. An increase in contrast and higher-order diffraction features are observed. In addition, excess-deficiency effects appear to be suppressed on energy filtering. This allows the fundamental physics of pattern formation to be interrogated and will enable a step change in the use of electron backscatter diffraction (EBSD) for crystal phase identification and the mapping of strain. The enhancement in the contrast in high-pass energy-filtered EBSD patterns is found to be stronger for lighter, less dense materials. The improved contrast for such materials will enable the application of the EBSD

High energy electron cooling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parkhomchuk, V.

1997-09-01

High energy electron cooling requires a very cold electron beam. The questions of using electron cooling with and without a magnetic field are presented for discussion at this workshop. The electron cooling method was suggested by G. Budker in the middle sixties. The original idea of the electron cooling was published in 1966. The design activities for the NAP-M project was started in November 1971 and the first run using a proton beam occurred in September 1973. The first experiment with both electron and proton beams was started in May 1974. In this experiment good result was achieved very closemore » to theoretical prediction for a usual two component plasma heat exchange.« less

Monte Carlo simulation of energy deposition by low-energy electrons in molecular hydrogen

NASA Technical Reports Server (NTRS)

Heaps, M. G.; Furman, D. R.; Green, A. E. S.

1975-01-01

A set of detailed atomic cross sections has been used to obtain the spatial deposition of energy by 1-20-eV electrons in molecular hydrogen by a Monte Carlo simulation of the actual trajectories. The energy deposition curve (energy per distance traversed) is quite peaked in the forward direction about the entry point for electrons with energies above the threshold of the electronic states, but the peak decreases and broadens noticeably as the electron energy decreases below 10 eV (threshold for the lowest excitable electronic state of H2). The curve also assumes a very symmetrical shape for energies below 10 eV, indicating the increasing importance of elastic collisions in determining the shape of the curve, although not the mode of energy deposition.

Femtosecond MeV Electron Energy-Loss Spectroscopy

DOE PAGES

Li, R. K.; Wang, X. J.

2017-11-09

Pump-probe electron energy-loss spectroscopy (EELS) with femtosecond temporal resolution will be a transformative research tool for studying nonequilibrium chemistry and electronic dynamics of matter. Here in this article, we propose a concept of femtosecond EELS utilizing mega-electron-volt electron beams from a radio-frequency (rf) photocathode source. The high acceleration gradient and high beam energy of the rf gun are critical to the generation of 10-fs electron beams, which enables an improvement of the temporal resolution by more than 1 order of magnitude beyond the state of the art. In our proposal, the “referencebeam technique” relaxes the energy stability requirement of themore » rf power source by roughly 2 orders of magnitude. The requirements for the electron-beam quality, photocathode, spectrometer, and detector are also discussed. Supported by particle-tracking simulations, we demonstrate the feasibility of achieving subelectron- volt energy resolution and approximately 10-fs temporal resolution with existing or near-future hardware performance.« less

Femtosecond MeV Electron Energy-Loss Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, R. K.; Wang, X. J.

Pump-probe electron energy-loss spectroscopy (EELS) with femtosecond temporal resolution will be a transformative research tool for studying nonequilibrium chemistry and electronic dynamics of matter. Here in this article, we propose a concept of femtosecond EELS utilizing mega-electron-volt electron beams from a radio-frequency (rf) photocathode source. The high acceleration gradient and high beam energy of the rf gun are critical to the generation of 10-fs electron beams, which enables an improvement of the temporal resolution by more than 1 order of magnitude beyond the state of the art. In our proposal, the “referencebeam technique” relaxes the energy stability requirement of themore » rf power source by roughly 2 orders of magnitude. The requirements for the electron-beam quality, photocathode, spectrometer, and detector are also discussed. Supported by particle-tracking simulations, we demonstrate the feasibility of achieving subelectron- volt energy resolution and approximately 10-fs temporal resolution with existing or near-future hardware performance.« less

Calculation on spectrum of direct DNA damage induced by low-energy electrons including dissociative electron attachment.

PubMed

Liu, Wei; Tan, Zhenyu; Zhang, Liming; Champion, Christophe

2017-03-01

In this work, direct DNA damage induced by low-energy electrons (sub-keV) is simulated using a Monte Carlo method. The characteristics of the present simulation are to consider the new mechanism of DNA damage due to dissociative electron attachment (DEA) and to allow determining damage to specific bases (i.e., adenine, thymine, guanine, or cytosine). The electron track structure in liquid water is generated, based on the dielectric response model for describing electron inelastic scattering and on a free-parameter theoretical model and the NIST database for calculating electron elastic scattering. Ionization cross sections of DNA bases are used to generate base radicals, and available DEA cross sections of DNA components are applied for determining DNA-strand breaks and base damage induced by sub-ionization electrons. The electron elastic scattering from DNA components is simulated using cross sections from different theoretical calculations. The resulting yields of various strand breaks and base damage in cellular environment are given. Especially, the contributions of sub-ionization electrons to various strand breaks and base damage are quantitatively presented, and the correlation between complex clustered DNA damage and the corresponding damaged bases is explored. This work shows that the contribution of sub-ionization electrons to strand breaks is substantial, up to about 40-70%, and this contribution is mainly focused on single-strand break. In addition, the base damage induced by sub-ionization electrons contributes to about 20-40% of the total base damage, and there is an evident correlation between single-strand break and damaged base pair A-T.

Electron energy distributions measured during electron beam/plasma interactions. [in E region

NASA Technical Reports Server (NTRS)

Jost, R. J.; Anderson, H. R.; Mcgarity, J. O.

1980-01-01

In the large vacuum facility at the NASA-Johnson Space Center an electron beam was projected 20 m parallel to B from a gun with variable accelerating potential (1.0 to 2.5 kV) to an aluminum target. The ionospheric neutral pressure and field were approximated. Beam electron energy distributions were measured directly using an electrostatic deflection analyzer and indirectly with a detector that responded to the X-rays produced by electron impact on the target. At low currents the distribution is sharply peaked at the acceleration potential. At high currents a beam plasma discharge occurs and electrons are redistributed in energy so that the former energy peak broadens to 10-15 percent FWHM with a strongly enhanced low energy tail. At the 10% of maximum point the energy spectrum ranges from less than 1/2 to 1.2 times the gun energy. The effect is qualitatively the same at all pitch angles and locations sampled.

Absolute cross section for low-energy-electron damage to condensed macromolecules: A case study of DNA

PubMed Central

Rezaee, Mohammad; Cloutier, Pierre; Bass, Andrew D.; Michaud, Marc; Hunting, Darel J.; Sanche, Léon

2013-01-01

Cross sections (CSs) for the interaction of low-energy electrons (LEE) with condensed macromolecules are essential parameters for accurate modeling of radiation-induced molecular decomposition and chemical synthesis. Electron irradiation of dry nanometer-scale macromolecular solid films has often been employed to measure CSs and other quantitative parameters for LEE interactions. Since such films have thicknesses comparable with electron thermalization distances, energy deposition varies throughout the film. Moreover, charge accumulation occurring inside the films shields a proportion of the macromolecules from electron irradiation. Such effects complicate the quantitative comparison of the CSs obtained in films of different thicknesses and limit the applicability of such measurements. Here, we develop a simple mathematical model, termed the molecular survival model, that employs a CS for a particular damage process together with an attenuation length related to the total CS, to investigate how a measured CS might be expected to vary with experimental conditions. As a case study, we measure the absolute CS for the formation of DNA strand breaks (SBs) by electron irradiation at 10 and 100 eV of lyophilized plasmid DNA films with thicknesses between 10 and 30 nm. The measurements are shown to depend strongly on the thickness and charging condition of the nanometer-scale films. Such behaviors are in accord with the model and support its validity. Via this analysis, the CS obtained for SB damage is nearly independent of film thickness and charging effects. In principle, this model can be adapted to provide absolute CSs for electron-induced damage or reactions occurring in other molecular solids across a wider range of experimental conditions. PMID:23030950

Electron-density descriptors as predictors in quantitative structure--activity/property relationships and drug design.

PubMed

Matta, Chérif F; Arabi, Alya A

2011-06-01

The use of electron density-based molecular descriptors in drug research, particularly in quantitative structure--activity relationships/quantitative structure--property relationships studies, is reviewed. The exposition starts by a discussion of molecular similarity and transferability in terms of the underlying electron density, which leads to a qualitative introduction to the quantum theory of atoms in molecules (QTAIM). The starting point of QTAIM is the topological analysis of the molecular electron-density distributions to extract atomic and bond properties that characterize every atom and bond in the molecule. These atomic and bond properties have considerable potential as bases for the construction of robust quantitative structure--activity/property relationships models as shown by selected examples in this review. QTAIM is applicable to the electron density calculated from quantum-chemical calculations and/or that obtained from ultra-high resolution x-ray diffraction experiments followed by nonspherical refinement. Atomic and bond properties are introduced followed by examples of application of each of these two families of descriptors. The review ends with a study whereby the molecular electrostatic potential, uniquely determined by the density, is used in conjunction with atomic properties to elucidate the reasons for the biological similarity of bioisosteres.

Low-energy electron-induced reactions in condensed matter

NASA Astrophysics Data System (ADS)

Arumainayagam, Christopher R.; Lee, Hsiao-Lu; Nelson, Rachel B.; Haines, David R.; Gunawardane, Richard P.

2010-01-01

The goal of this review is to discuss post-irradiation analysis of low-energy (≤50 eV) electron-induced processes in nanoscale thin films. Because electron-induced surface reactions in monolayer adsorbates have been extensively reviewed, we will instead focus on low-energy electron-induced reactions in multilayer adsorbates. The latter studies, involving nanoscale thin films, serve to elucidate the pivotal role that the low-energy electron-induced reactions play in high-energy radiation-induced chemical reactions in condensed matter. Although electron-stimulated desorption (ESD) experiments conducted during irradiation have yielded vital information relevant to primary or initial electron-induced processes, we wish to demonstrate in this review that analyzing the products following low-energy electron irradiation can provide new insights into radiation chemistry. This review presents studies of electron-induced reactions in nanoscale films of molecular species such as oxygen, nitrogen trifluoride, water, alkanes, alcohols, aldehydes, ketones, carboxylic acids, nitriles, halocarbons, alkane and phenyl thiols, thiophenes, ferrocene, amino acids, nucleotides, and DNA using post-irradiation techniques such as temperature-programmed desorption (TPD), reflection-absorption infrared spectroscopy (RAIRS), X-ray photoelectron spectroscopy (XPS), high-resolution electron energy loss spectroscopy (HREELS), gel electrophoresis, and microarray fluorescence. Post-irradiation temperature-programmed desorption, in particular, has been shown to be useful in identifying labile radiolysis products as demonstrated by the first identification of methoxymethanol as a reaction product of methanol radiolysis. Results of post-irradiation studies have been used not only to identify radiolysis products, but also to determine the dynamics of electron-induced reactions. For example, studies of the radiolysis yield as a function of incident electron energy have shown that dissociative

Remineralization of enamel subsurface lesions with casein phosphopeptide-amorphous calcium phosphate: A quantitative energy dispersive X-ray analysis using scanning electron microscopy: An in vitro study

PubMed Central

Hegde, Mithra N; Moany, Anu

2012-01-01

Aim: The objective of this study was to quantitatively evaluate the remineralization potential of casein phosphopeptide-amor-phous calcium phosphate paste on enamel subsurface lesions using scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX). Materials and Methods: Ninety enamel specimens were prepared from extracted human molars. All specimens were evaluated for mineral content (% weight) using SEM-EDX. The specimens were placed in demineralizing solution for four days to produce artificial carious lesions. The mineral content (calcium/phosphorus ratios, Ca/P ratios) was remeasured using SEM-EDX. The specimens were then randomly assigned to five study groups and one control group of 15 specimens per group. Except for the control group, all group specimens were incubated in remineralizing paste (CPP-ACP paste) for 7, 14, 21, 28, and 35 days twice daily for three minutes. The control group received no treatment with remineralizing paste. All the 90 specimens were stored in artificial saliva at 37°C. After remineralization, the mineral content (% weight) of the samples was measured using SEM-EDX. Results: All the study groups showed very highly significant differences between Ca/P ratios of the demineralized and remineralized samples. There was no significant difference seen in the control group. Conclusion: CPP-ACP paste could significantly remineralize the artificial enamel subsurface lesions in vitro: the remineralizing rates increasing with the time for which the samples were kept in the remineralizing paste. Energy dispersive X-ray analysis is an efficient way to quantitatively assess the changes in mineral content during demineralization and in vitro remineralization processes. PMID:22368338

High Energy Electron Detection with ATIC

NASA Technical Reports Server (NTRS)

Chang, J.; Schmidt, W. K. H.; Adams, James H., Jr.; Ahn, H.; Ampe, J.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

The ATIC (Advanced Thin Ionization Calorimeter) balloon-borne ionization calorimeter is well suited to record and identify high energy cosmic ray electrons. The instrument was exposed to high-energy beams at CERN H2 bean-dine in September of 1999. We have simulated the performance of the instrument, and compare the simulations with actual high energy electron exposures at the CERN accelerator. Simulations and measurements do not compare exactly, in detail, but overall the simulations have predicted actual measured behavior quite well.

Electron energy recovery system for negative ion sources

DOEpatents

Dagenhart, W.K.; Stirling, W.L.

1979-10-25

An electron energy recovery system for negative ion sources is provided. The system, employing crossed electric and magnetic fields, separates the electrons from the ions as they are extracted from the ion source plasma generator and before the ions are accelerated to their full energy. With the electric and magnetic fields oriented 90/sup 0/ to each other, the electrons remain at approximately the electrical potential at which they were generated. The electromagnetic forces cause the ions to be accelerated to the full accelerating supply voltage energy while being deflected through an angle of less than 90/sup 0/. The electrons precess out of the accelerating field region into an electron recovery region where they are collected at a small fraction of the full accelerating supply energy. It is possible, by this method, to collect > 90% of the electrons extracted along with the negative ions from a negative ion source beam at < 4% of full energy.

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.

Application of relativistic electrons for the quantitative analysis of trace elements

NASA Astrophysics Data System (ADS)

Hoffmann, D. H. H.; Brendel, C.; Genz, H.; Löw, W.; Richter, A.

1984-04-01

Particle induced X-ray emission methods (PIXE) have been extended to relativistic electrons to induce X-ray emission (REIXE) for quantitative trace-element analysis. The electron beam (20 ≤ E0≤ 70 MeV) was supplied by the Darmstadt electron linear accelerator DALINAC. Systematic measurements of absolute K-, L- and M-shell ionization cross sections revealed a scaling behaviour of inner-shell ionization cross sections from which X-ray production cross sections can be deduced for any element of interest for a quantitative sample investigation. Using a multielemental mineral monazite sample from Malaysia the sensitivity of REIXE is compared to well established methods of trace-element analysis like proton- and X-ray-induced X-ray fluorescence analysis. The achievable detection limit for very heavy elements amounts to about 100 ppm for the REIXE method. As an example of an application the investigation of a sample prepared from manganese nodules — picked up from the Pacific deep sea — is discussed, which showed the expected high mineral content of Fe, Ni, Cu and Ti, although the search for aliquots of Pt did not show any measurable content within an upper limit of 250 ppm.

Database for Simulation of Electron Spectra for Surface Analysis (SESSA)Database for Simulation of Electron Spectra for Surface Analysis (SESSA)

National Institute of Standards and Technology Data Gateway

SRD 100 Database for Simulation of Electron Spectra for Surface Analysis (SESSA)Database for Simulation of Electron Spectra for Surface Analysis (SESSA) (PC database for purchase)   This database has been designed to facilitate quantitative interpretation of Auger-electron and X-ray photoelectron spectra and to improve the accuracy of quantitation in routine analysis. The database contains all physical data needed to perform quantitative interpretation of an electron spectrum for a thin-film specimen of given composition. A simulation module provides an estimate of peak intensities as well as the energy and angular distributions of the emitted electron flux.

Attainment of Electron Beam Suitable for Medium Energy Electron Cooling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seletskiy, Sergei M.

Electron cooling of charged particle beams is a well-established technique at electron energies of up to 300 keV. However, up to the present time the advance of electron cooling to the MeV-range energies has remained a purely theoretical possibility. The electron cooling project at Fermilab has recently demonstrated the ¯rst cooling of 8.9 GeV/c antiprotons in the Recycler ring, and therefore, has proved the validity of the idea of relativistic electron cool- ing. The Recycler Electron Cooler (REC) is the key component of the Teva- tron Run II luminosity upgrade project. Its performance depends critically on the quality of electronmore » beam. A stable electron beam of 4.3 MeV car- rying 0.5 A of DC current is required. The beam suitable for the Recycler Electron Cooler must have an angular spread not exceeding 200 ¹rad. The full-scale prototype of the REC was designed, built and tested at Fermilab in the Wideband laboratory to study the feasibility of attaining the high-quality electron beam. In this thesis I describe various aspects of development of the Fermilab electron cooling system, and the techniques used to obtain the electron beam suitable for the cooling process. In particular I emphasize those aspects of the work for which I was principally responsible.« less

Development of an electron-ion coincidence apparatus for molecular-frame electron energy loss spectroscopy studies

NASA Astrophysics Data System (ADS)

Watanabe, Noboru; Hirayama, Tsukasa; Yamada, So; Takahashi, Masahiko

2018-04-01

We report details of an electron-ion coincidence apparatus, which has been developed for molecular-frame electron energy loss spectroscopy studies. The apparatus is mainly composed of a pulsed electron gun, an energy-dispersive electron spectrometer, and an ion momentum imaging spectrometer. Molecular-orientation dependence of the high-energy electron scattering cross section can be examined by conducting measurements of vector correlation between the momenta of the scattered electron and fragment ion. Background due to false coincidences is significantly reduced by introducing a pulsed electron beam and pulsing scheme of ion extraction. The experimental setup has been tested by measuring the inner-shell excitation of N2 at an incident electron energy of 1.5 keV and a scattering angle of 10.2°.

Energy dependence of lithium fluoride dosemeter for high energy electrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antoku, S.; Sunayashiki, T.; Takeoka, S.

1973-11-01

A lithium fluoride and a Fricke dosemeter have been exposed simultaneously to /sup 60/Co gamma -rays and 10, 20, and 30 MeV electrons to study the energy dependence of the lithium fluoride dosemeter for high-energy electrons, with particular reference to possible significant reductions in the sensitivity of LiF phosphors for electrons as compared with /sup 60/Co gamma - rays. In the present study, the direct comparison excluded errors resulting from uncertainties about ion recombination and conversion factors from roentgens to rads for ionization chambers. The dosemeters were exposed to approximately 5000 rads of each radiation at the appropriate peak depthmore » in a water phantom. Corrections for the supra-linear response for LiF were made using a dose response curve for /sup 60/Co gamma -rays. The three types of LiF phosphor examined did not exhibit any energy dependence for electrons compared with /sup 60/Co gamma - rays. Within the statistical uncertainty (~3%) for the experiment. (UK)« less

An energy-dependent electron backscattering coefficient

NASA Astrophysics Data System (ADS)

Williamson, W., Jr.; Antolak, A. J.; Meredith, R. J.

1987-05-01

An energy-dependent electron backscattering coefficient is derived based on the continuous slowing down approximation and the Bethe stopping power. Backscattering coefficients are given for 10-50-keV electrons incident on bulk and thin-film aluminum, silver, and gold targets. The results are compared with the Everhart theory and empirical fits to experimental data. The energy-dependent theory agrees better with experimental work.

Generation of Low-Energy High-Current Electron Beams in Plasma-Anode Electron Guns

NASA Astrophysics Data System (ADS)

Ozur, G. E.; Proskurovsky, D. I.

2018-01-01

This paper is a review of studies on the generation of low-energy high-current electron beams in electron guns with a plasma anode and an explosive-emission cathode. The problems related to the initiation of explosive electron emission under plasma and the formation and transport of high-current electron beams in plasma-filled systems are discussed consecutively. Considerable attention is given to the nonstationary effects that occur in the space charge layers of plasma. Emphasis is also placed on the problem of providing a uniform energy density distribution over the beam cross section, which is of critical importance in using electron beams of this type for surface treatment of materials. Examples of facilities based on low-energy high-current electron beam sources are presented and their applications in materials science and practice are discussed.

Retarding field energy analyzer for high energy pulsed electron beam measurements.

PubMed

Hu, Jing; Rovey, Joshua L; Zhao, Wansheng

2017-01-01

A retarding field energy analyzer (RFEA) designed specifically for high energy pulsed electron beam measurements is described in this work. By proper design of the entrance grid, attenuation grid, and beam collector, this RFEA is capable of determining the time-resolved energy distribution of high energy pulsed electron beams normally generated under "soft vacuum" environment. The performance of the RFEA is validated by multiple tests of the leakage current, attenuation coefficient, and response time. The test results show that the retarding potential in the RFEA can go up to the same voltage as the electron beam source, which is 20 kV for the maximum in this work. Additionally, an attenuation coefficient of 4.2 is obtained in the RFEA while the percent difference of the rise time of the electron beam pulse before and after attenuation is lower than 10%. When compared with a reference source, the percent difference of the RFEA response time is less than 10% for fall times greater than 35 ns. Finally, the test results of the 10 kV pseudospark-based pulsed electron beam currents collected under varying retarding potentials are presented in this paper.

Quantitative analysis of intermolecular interactions in orthorhombic rubrene

DOE PAGES

Hathwar, Venkatesha R.; Sist, Mattia; Jørgensen, Mads R. V.; ...

2015-08-14

Rubrene is one of the most studied organic semiconductors to date due to its high charge carrier mobility which makes it a potentially applicable compound in modern electronic devices. Previous electronic device characterizations and first principles theoretical calculations assigned the semiconducting properties of rubrene to the presence of a large overlap of the extended π-conjugated core between molecules. We present here the electron density distribution in rubrene at 20 K and at 100 K obtained using a combination of high-resolution X-ray and neutron diffraction data. The topology of the electron density and energies of intermolecular interactions are studied quantitatively. Specifically,more » the presence of C π...C πinteractions between neighbouring tetracene backbones of the rubrene molecules is experimentally confirmed from a topological analysis of the electron density, Non-Covalent Interaction (NCI) analysis and the calculated interaction energy of molecular dimers. A significant contribution to the lattice energy of the crystal is provided by H—H interactions. The electron density features of H—H bonding, and the interaction energy of molecular dimers connected by H—H interaction clearly demonstrate an importance of these weak interactions in the stabilization of the crystal structure. Finally, the quantitative nature of the intermolecular interactions is virtually unchanged between 20 K and 100 K suggesting that any changes in carrier transport at these low temperatures would have a different origin. The obtained experimental results are further supported by theoretical calculations.« less

Properties of the electron cloud in a high-energy positron and electron storage ring

DOE PAGES

Harkay, K. C.; Rosenberg, R. A.

2003-03-20

Low-energy, background electrons are ubiquitous in high-energy particle accelerators. Under certain conditions, interactions between this electron cloud and the high-energy beam can give rise to numerous effects that can seriously degrade the accelerator performance. These effects range from vacuum degradation to collective beam instabilities and emittance blowup. Although electron-cloud effects were first observed two decades ago in a few proton storage rings, they have in recent years been widely observed and intensely studied in positron and proton rings. Electron-cloud diagnostics developed at the Advanced Photon Source enabled for the first time detailed, direct characterization of the electron-cloud properties in amore » positron and electron storage ring. From in situ measurements of the electron flux and energy distribution at the vacuum chamber wall, electron-cloud production mechanisms and details of the beam-cloud interaction can be inferred. A significant longitudinal variation of the electron cloud is also observed, due primarily to geometrical details of the vacuum chamber. Furthermore, such experimental data can be used to provide realistic limits on key input parameters in modeling efforts, leading ultimately to greater confidence in predicting electron-cloud effects in future accelerators.« less

Electron energy and electron trajectories in an inverse free-electron laser accelerator based on a novel electrostatic wiggler

NASA Astrophysics Data System (ADS)

Nikrah, M.; Jafari, S.

2016-06-01

We expand here a theory of a high-gradient laser-excited electron accelerator based on an inverse free-electron laser (inverse-FEL), but with innovations in the structure and design. The electrostatic wiggler used in our scheme, namely termed the Paul wiggler, is generated by segmented cylindrical electrodes with applied oscillatory voltages {{V}\\text{osc}}(t) over {{90}\\circ} segments. The inverse-FEL interaction can be described by the equations that govern the electron motion in the combined fields of both the laser pulse and Paul wiggler field. A numerical study of electron energy and electron trajectories has been made using the fourth-order Runge-Kutta method. The results indicate that the electron attains a considerable energy at short distances in this device. It is found that if the electron has got sufficient suitable wiggler amplitude intensities, it can not only gain higher energy in longer distances, but also can retain it even after the passing of the laser pulse. In addition, the results reveal that the electron energy gains different peaks for different initial axial velocities, so that a suitable small initial axial velocity of e-beam produces substantially high energy gain. With regard to the transverse confinement of the electron beam in a Paul wiggler, there is no applied axial guide magnetic field in this device.

An electronic nose for quantitative determination of gas concentrations

NASA Astrophysics Data System (ADS)

Jasinski, Grzegorz; Kalinowski, Paweł; Woźniak, Łukasz

2016-11-01

The practical application of human nose for fragrance recognition is severely limited by the fact that our sense of smell is subjective and gets tired easily. Consequently, there is considerable need for an instrument that can be a substitution of the human sense of smell. Electronic nose devices from the mid 1980s are used in growing number of applications. They comprise an array of several electrochemical gas sensors with partial specificity and a pattern recognition algorithms. Most of such systems, however, is only used for qualitative measurements. In this article usage of such system in quantitative determination of gas concentration is demonstrated. Electronic nose consist of a sensor array with eight commercially available Taguchi type gas sensor. Performance of three different pattern recognition algorithms is compared, namely artificial neural network, partial least squares regression and support vector machine regression. The electronic nose is used for ammonia and nitrogen dioxide concentration determination.

A simple energy filter for low energy electron microscopy/photoelectron emission microscopy instruments.

PubMed

Tromp, R M; Fujikawa, Y; Hannon, J B; Ellis, A W; Berghaus, A; Schaff, O

2009-08-05

Addition of an electron energy filter to low energy electron microscopy (LEEM) and photoelectron emission microscopy (PEEM) instruments greatly improves their analytical capabilities. However, such filters tend to be quite complex, both electron optically and mechanically. Here we describe a simple energy filter for the existing IBM LEEM/PEEM instrument, which is realized by adding a single scanning aperture slit to the objective transfer optics, without any further modifications to the microscope. This energy filter displays a very high energy resolution ΔE/E = 2 × 10(-5), and a non-isochromaticity of ∼0.5 eV/10 µm. The setup is capable of recording selected area electron energy spectra and angular distributions at 0.15 eV energy resolution, as well as energy filtered images with a 1.5 eV energy pass band at an estimated spatial resolution of ∼10 nm. We demonstrate the use of this energy filter in imaging and spectroscopy of surfaces using a laboratory-based He I (21.2 eV) light source, as well as imaging of Ag nanowires on Si(001) using the 4 eV energy loss Ag plasmon.

Energy-filtered cold electron transport at room temperature.

PubMed

Bhadrachalam, Pradeep; Subramanian, Ramkumar; Ray, Vishva; Ma, Liang-Chieh; Wang, Weichao; Kim, Jiyoung; Cho, Kyeongjae; Koh, Seong Jin

2014-09-10

Fermi-Dirac electron thermal excitation is an intrinsic phenomenon that limits functionality of various electron systems. Efforts to manipulate electron thermal excitation have been successful when the entire system is cooled to cryogenic temperatures, typically <1 K. Here we show that electron thermal excitation can be effectively suppressed at room temperature, and energy-suppressed electrons, whose energy distribution corresponds to an effective electron temperature of ~45 K, can be transported throughout device components without external cooling. This is accomplished using a discrete level of a quantum well, which filters out thermally excited electrons and permits only energy-suppressed electrons to participate in electron transport. The quantum well (~2 nm of Cr2O3) is formed between source (Cr) and tunnelling barrier (SiO2) in a double-barrier-tunnelling-junction structure having a quantum dot as the central island. Cold electron transport is detected from extremely narrow differential conductance peaks in electron tunnelling through CdSe quantum dots, with full widths at half maximum of only ~15 mV at room temperature.

Energy-filtered cold electron transport at room temperature

PubMed Central

Bhadrachalam, Pradeep; Subramanian, Ramkumar; Ray, Vishva; Ma, Liang-Chieh; Wang, Weichao; Kim, Jiyoung; Cho, Kyeongjae; Koh, Seong Jin

2014-01-01

Fermi-Dirac electron thermal excitation is an intrinsic phenomenon that limits functionality of various electron systems. Efforts to manipulate electron thermal excitation have been successful when the entire system is cooled to cryogenic temperatures, typically <1 K. Here we show that electron thermal excitation can be effectively suppressed at room temperature, and energy-suppressed electrons, whose energy distribution corresponds to an effective electron temperature of ~45 K, can be transported throughout device components without external cooling. This is accomplished using a discrete level of a quantum well, which filters out thermally excited electrons and permits only energy-suppressed electrons to participate in electron transport. The quantum well (~2 nm of Cr2O3) is formed between source (Cr) and tunnelling barrier (SiO2) in a double-barrier-tunnelling-junction structure having a quantum dot as the central island. Cold electron transport is detected from extremely narrow differential conductance peaks in electron tunnelling through CdSe quantum dots, with full widths at half maximum of only ~15 mV at room temperature. PMID:25204839

Laboratory studies on low-energy electron penetration depths into amorphous ice - consequence to astrobiology on icy surfaces

NASA Astrophysics Data System (ADS)

Gudipati, M. S.; Li, I.; Lignell, A. A.

2009-12-01

Penetration of electrons through icy surfaces plays an important role in radiation processing of solar system icy bodies. However, to date, there is no quantitative data available on the penetration depths of electrons through cryogenic water-ices. Penetration of high-energy incident electrons also results in the in-situ formation of secondary low-energy electrons, such as on the surface of Europa (Herring-Captain et al., 2005; Johnson et al., 2004). Low-energy electrons can also be produced through photoionization process such as on comet surfaces, or through bombardment by solar wind on icy surfaces (Bodewits et al., 2004). Present models use the laboratory penetration data of high-energy (>10 keV) electrons through silicon as a proxy for the ice (Cooper et al., 2001), normalized by the density of the medium. So far no laboratory studies have been conducted that deal with the penetration of electrons through amorphous or crystalline ices. In order to address this issue, we adopted a new experimental strategy by using aromatic molecules as probes. To begin with, we carried out systematic studies on the penetration depths of low-energy electrons (5 eV - 2 keV) through amorphous ice films of defined thickness at cryogenic temperatures (5 - 30 K). The results of these experiments will be analyzed and their relevance to survival of organic material on solar system icy surfaces will be presented. References: Bodewits, D., et al., 2004. X-ray and Far-Ultraviolet emission from comets: Relevant charge exchange processes. Physica Scripta. 70, C17-C20. Cooper, J. F., et al., 2001. Energetic ion and electron irradiation of the icy Galilean satellites. Icarus. 149, 133-159. Herring-Captain, J., et al., 2005. Low-energy (5-250 eV) electron-stimulated desorption of H+, H2+, and H+(H2O)nfrom low-temperature water ice surfaces. Physical Review B. 72, 035431-10. Johnson, R. E., et al., Radiation Effects on the Surfaces of the Galilean Satellites. In: F. Bagenal, et al., Eds

Housing Electrons: Relating Quantum Numbers, Energy Levels, and Electron Configurations.

ERIC Educational Resources Information Center

Garofalo, Anthony

1997-01-01

Presents an activity that combines the concepts of quantum numbers and probability locations, energy levels, and electron configurations in a concrete, hands-on way. Uses model houses constructed out of foam board and colored beads to represent electrons. (JRH)

Energy Conversion Mechanism for Electron Perpendicular Energy in High Guide-Field Reconnection

NASA Astrophysics Data System (ADS)

Guo, Xuehan; Horiuchi, Ritoku; Kaminou, Yasuhiro; Cheng, Frank; Ono, Yasushi

2016-10-01

The energy conversion mechanism for electron perpendicular energy, both the thermal and the kinetic energy, is investigated by means of two-dimensional, full-particle simulations in an open system. It is shown that electron perpendicular heating is mainly due to the breaking of magnetic moment conservation in separatrix region because the charge separation generates intense variation of electric field within the electron Larmor radius. Meanwhile, electron perpendicular acceleration takes place manly due to the polarization drift term as well as the curvature drift term of E . u⊥ in the downstream near the X-point. The enhanced electric field due to the charge separation there results in a significant effect of the polarization drift term on the dissipation of magnetic energy within the ion inertia length in the downstream. Japan Society for the Promotion of Science (JSPS) Fellows 15J03758.

Microstructural study of the nickel-base alloy WAZ-20 using qualitative and quantitative electron optical techniques

NASA Technical Reports Server (NTRS)

Young, S. G.

1973-01-01

The NASA nickel-base alloy WAZ-20 was analyzed by advanced metallographic techniques to qualitatively and quantitatively characterize its phases and stability. The as-cast alloy contained primary gamma-prime, a coarse gamma-gamma prime eutectic, a gamma-fine gamma prime matrix, and MC carbides. A specimen aged at 870 C for 1000 hours contained these same constituents and a few widely scattered high W particles. No detrimental phases (such as sigma or mu) were observed. Scanning electron microscope, light metallography, and replica electron microscope methods are compared. The value of quantitative electron microprobe techniques such as spot and area analysis is demonstrated.

Electron energy distribution function, effective electron temperature, and dust charge in the temporal afterglow of a plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denysenko, I. B.; Azarenkov, N. A.; Kersten, H.

2016-05-15

Analytical expressions describing the variation of electron energy distribution function (EEDF) in an afterglow of a plasma are obtained. Especially, the case when the electron energy loss is mainly due to momentum-transfer electron-neutral collisions is considered. The study is carried out for different EEDFs in the steady state, including Maxwellian and Druyvesteyn distributions. The analytical results are not only obtained for the case when the rate for momentum-transfer electron-neutral collisions is independent on electron energy but also for the case when the collisions are a power function of electron energy. Using analytical expressions for the EEDF, the effective electron temperaturemore » and charge of the dust particles, which are assumed to be present in plasma, are calculated for different afterglow durations. An analytical expression for the rate describing collection of electrons by dust particles for the case when the rate for momentum-transfer electron-neutral collisions is independent on electron energy is also derived. The EEDF profile and, as a result, the effective electron temperature and dust charge are sufficiently different in the cases when the rate for momentum-transfer electron-neutral collisions is independent on electron energy and when the rate is a power function of electron energy.« less

The Energy Spectrum of Jovian Electrons in Interplanetary Space

NASA Technical Reports Server (NTRS)

Christon, S. P.; Cummings, A. C.; Stone, E. C.; Webber, W. R.

1985-01-01

The energy spectrum of electrons with energies approx 10 to approx 180 MeV measured with the electron telescope on the Voyager 1 and 2 spacecraft in interplanetary space from 1978 to 1983 is studied. The kinetic energy of electrons is determined by double dE/dx measurements from the first two detectors (D sub 1, D sub 2) of a stack of eight solid state detectors and by the range of particle penetration into the remaining six detectors (D sub 3 to D sub 8) which are interleaved with tungsten absorbers. From 1978 to 1983 (radial range approximately 2 to a pproximately 12 AU) electrons of Jovian origin were clearly observable for electrons stopping in D(sub 3(E approximately greater than 4 MeV)) and in D(sub 4 (E approximately greater than 8 MeV)). For electrons stopping in D(sub 5(E approximately greather than 12 MeV)), the jovian flux dominated the galactic electron flux for a period of approximately one year near the encounter with Jupiter. Jovian electrons were also observed in D(sub 6(E approximately greater than 21 MeV)) but not in D(sub 7(E approximately greater than 28 MeV)). A detailed interpretation of the electron variations in all energy channels depends on an accurate subtraction of background induced by energetic protons of a few 100 MeV. This substraction is facilitated by laboratory calibration results at several energies. Further results on the differential energy spectrum of Jovian electrons and limits on the maximum detected energies will be reported.

Multifunctional Skin-like Electronics for Quantitative, Clinical Monitoring of Cutaneous Wound Healing

PubMed Central

Hattori, Yoshiaki; Falgout, Leo; Lee, Woosik; Jung, Sung-Young; Poon, Emily; Lee, Jung Woo; Na, Ilyoun; Geisler, Amelia; Sadhwani, Divya; Zhang, Yihui; Su, Yewang; Wang, Xiaoqi; Liu, Zhuangjian; Xia, Jing; Cheng, Huanyu; Webb, R. Chad; Bonifas, Andrew P.; Won, Philip; Jeong, Jae-Woong; Jang, Kyung-In; Song, Young Min; Nardone, Beatrice; Nodzenski, Michael; Fan, Jonathan A.; Huang, Yonggang; West, Dennis P.; Paller, Amy S.; Alam, Murad

2014-01-01

Non-invasive, biomedical devices have the potential to provide important, quantitative data for the assessment of skin diseases and wound healing. Traditional methods either rely on qualitative visual and tactile judgments of a professional and/or data obtained using instrumentation with forms that do not readily allow intimate integration with sensitive skin near a wound site. Here we report a skin-like electronics platform that can softly and reversibly laminate perilesionally at wounds to provide highly accurate, quantitative data of relevance to the management of surgical wound healing. Clinical studies on patients using thermal sensors and actuators in fractal layouts provide precise time-dependent mapping of temperature and thermal conductivity of the skin near the wounds. Analytical and simulation results establish the fundamentals of the sensing modalities, the mechanics of the system, and strategies for optimized design. The use of this type of ‘epidermal’ electronics system in a realistic, clinical setting with human subjects establishes a set of practical procedures in disinfection, reuse, and protocols for quantitative measurement. The results have the potential to address important unmet needs in chronic wound management. PMID:24668927

Multifunctional skin-like electronics for quantitative, clinical monitoring of cutaneous wound healing

DOE PAGES

Hattori, Yoshiaki; Falgout, Leo; Lee, Woosik; ...

2014-03-26

Non-invasive, biomedical devices have the potential to provide important, quantitative data for the assessment of skin diseases and wound healing. Traditional methods either rely on qualitative visual and tactile judgments of a professional and/or data obtained using instrumentation with forms that do not readily allow intimate integration with sensitive skin near a wound site. In this paper, an electronic sensor platform that can softly and reversibly laminate perilesionally at wounds to provide highly accurate, quantitative data of relevance to the management of surgical wound healing is reported. Clinical studies on patients using thermal sensors and actuators in fractal layouts providemore » precise time-dependent mapping of temperature and thermal conductivity of the skin near the wounds. Analytical and simulation results establish the fundamentals of the sensing modalities, the mechanics of the system, and strategies for optimized design. The use of this type of “epidermal” electronics system in a realistic clinical setting with human subjects establishes a set of practical procedures in disinfection, reuse, and protocols for quantitative measurement. Finally, the results have the potential to address important unmet needs in chronic wound management.« less

Multifunctional skin-like electronics for quantitative, clinical monitoring of cutaneous wound healing.

PubMed

Hattori, Yoshiaki; Falgout, Leo; Lee, Woosik; Jung, Sung-Young; Poon, Emily; Lee, Jung Woo; Na, Ilyoun; Geisler, Amelia; Sadhwani, Divya; Zhang, Yihui; Su, Yewang; Wang, Xiaoqi; Liu, Zhuangjian; Xia, Jing; Cheng, Huanyu; Webb, R Chad; Bonifas, Andrew P; Won, Philip; Jeong, Jae-Woong; Jang, Kyung-In; Song, Young Min; Nardone, Beatrice; Nodzenski, Michael; Fan, Jonathan A; Huang, Yonggang; West, Dennis P; Paller, Amy S; Alam, Murad; Yeo, Woon-Hong; Rogers, John A

2014-10-01

Non-invasive, biomedical devices have the potential to provide important, quantitative data for the assessment of skin diseases and wound healing. Traditional methods either rely on qualitative visual and tactile judgments of a professional and/or data obtained using instrumentation with forms that do not readily allow intimate integration with sensitive skin near a wound site. Here, an electronic sensor platform that can softly and reversibly laminate perilesionally at wounds to provide highly accurate, quantitative data of relevance to the management of surgical wound healing is reported. Clinical studies on patients using thermal sensors and actuators in fractal layouts provide precise time-dependent mapping of temperature and thermal conductivity of the skin near the wounds. Analytical and simulation results establish the fundamentals of the sensing modalities, the mechanics of the system, and strategies for optimized design. The use of this type of "epidermal" electronics system in a realistic clinical setting with human subjects establishes a set of practical procedures in disinfection, reuse, and protocols for quantitative measurement. The results have the potential to address important unmet needs in chronic wound management. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Validation of Ground-based Optical Estimates of Auroral Electron Precipitation Energy Deposition

NASA Astrophysics Data System (ADS)

Hampton, D. L.; Grubbs, G. A., II; Conde, M.; Lynch, K. A.; Michell, R.; Zettergren, M. D.; Samara, M.; Ahrns, M. J.

2017-12-01

One of the major energy inputs into the high latitude ionosphere and mesosphere is auroral electron precipitation. Not only does the kinetic energy get deposited, the ensuing ionization in the E and F-region ionosphere modulates parallel and horizontal currents that can dissipate in the form of Joule heating. Global models to simulate these interactions typically use electron precipitation models that produce a poor representation of the spatial and temporal complexity of auroral activity as observed from the ground. This is largely due to these precipitation models being based on averages of multiple satellite overpasses separated by periods much longer than typical auroral feature durations. With the development of regional and continental observing networks (e.g. THEMIS ASI), the possibility of ground-based optical observations producing quantitative estimates of energy deposition with temporal and spatial scales comparable to those known to be exhibited in auroral activity become a real possibility. Like empirical precipitation models based on satellite overpasses such optics-based estimates are subject to assumptions and uncertainties, and therefore require validation. Three recent sounding rocket missions offer such an opportunity. The MICA (2012), GREECE (2014) and Isinglass (2017) missions involved detailed ground based observations of auroral arcs simultaneously with extensive on-board instrumentation. These have afforded an opportunity to examine the results of three optical methods of determining auroral electron energy flux, namely 1) ratio of auroral emissions, 2) green line temperature vs. emission altitude, and 3) parametric estimates using white-light images. We present comparisons from all three methods for all three missions and summarize the temporal and spatial scales and coverage over which each is valid.

The interaction of low-energy electrons with fructose molecules

NASA Astrophysics Data System (ADS)

Chernyshova, I. V.; Kontrosh, E. E.; Markush, P. P.; Shpenik, O. B.

2017-11-01

Using a hypocycloidal electronic spectrometer, the interactions of low energy electrons (0-8.50 eV) with fructose molecules, namely, electron scattering and dissociative attachment, are studied. The results of these studies showed that the fragmentation of fructose molecules occurs effectively even at an electron energy close to zero. In the total electron-scattering cross section by molecules, resonance features (at energies 3.10 and 5.00 eV) were first observed near the formation thresholds of light ion fragments OH- and H-. The correlation of the features observed in the cross sections of electron scattering and dissociative attachment is analyzed.

Effects of instrument imperfections on quantitative scanning transmission electron microscopy.

PubMed

Krause, Florian F; Schowalter, Marco; Grieb, Tim; Müller-Caspary, Knut; Mehrtens, Thorsten; Rosenauer, Andreas

2016-02-01

Several instrumental imperfections of transmission electron microscopes are characterized and their effects on the results of quantitative scanning electron microscopy (STEM) are investigated and quantified using simulations. Methods to either avoid influences of these imperfections during acquisition or to include them in reference calculations are proposed. Particularly, distortions inflicted on the diffraction pattern by an image-aberration corrector can cause severe errors of more than 20% if not accounted for. A procedure for their measurement is proposed here. Furthermore, afterglow phenomena and nonlinear behavior of the detector itself can lead to incorrect normalization of measured intensities. Single electrons accidentally impinging on the detector are another source of error but can also be exploited for threshold-less calibration of STEM images to absolute dose, incident beam current determination and measurement of the detector sensitivity. Copyright © 2015 Elsevier B.V. All rights reserved.

Magnetosphere-Ionosphere Energy Interchange in the Electron Diffuse Aurora

NASA Technical Reports Server (NTRS)

Khazanov, George V.; Glocer, Alex; Himwich, E. W.

2014-01-01

The diffuse aurora has recently been shown to be a major contributor of energy flux into the Earth's ionosphere. Therefore, a comprehensive theoretical analysis is required to understand its role in energy redistribution in the coupled ionosphere-magnetosphere system. In previous theoretical descriptions of precipitated magnetospheric electrons (E is approximately 1 keV), the major focus has been the ionization and excitation rates of the neutral atmosphere and the energy deposition rate to thermal ionospheric electrons. However, these precipitating electrons will also produce secondary electrons via impact ionization of the neutral atmosphere. This paper presents the solution of the Boltzman-Landau kinetic equation that uniformly describes the entire electron distribution function in the diffuse aurora, including the affiliated production of secondary electrons (E greater than 600 eV) and their ionosphere-magnetosphere coupling processes. In this article, we discuss for the first time how diffuse electron precipitation into the atmosphere and the associated secondary electron production participate in ionosphere-magnetosphere energy redistribution.

OPTIMAL ELECTRON ENERGIES FOR DRIVING CHROMOSPHERIC EVAPORATION IN SOLAR FLARES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reep, J. W.; Bradshaw, S. J.; Alexander, D., E-mail: jr665@cam.ac.uk, E-mail: stephen.bradshaw@rice.edu, E-mail: dalex@rice.edu

2015-08-01

In the standard model of solar flares, energy deposition by a beam of electrons drives strong chromospheric evaporation leading to a significantly denser corona and much brighter emission across the spectrum. Chromospheric evaporation was examined in great detail by Fisher et al., who described a distinction between two different regimes, termed explosive and gentle evaporation. In this work, we examine the importance of electron energy and stopping depths on the two regimes and on the atmospheric response. We find that with explosive evaporation, the atmospheric response does not depend strongly on electron energy. In the case of gentle evaporation, lowermore » energy electrons are significantly more efficient at heating the atmosphere and driving up-flows sooner than higher energy electrons. We also find that the threshold between explosive and gentle evaporation is not fixed at a given beam energy flux, but also depends strongly on the electron energy and duration of heating. Further, at low electron energies, a much weaker beam flux is required to drive explosive evaporation.« less

Measurement of the dynamic charge response of materials using low-energy, momentum-resolved electron energy-loss spectroscopy (M-EELS)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Husain, Ali A.; Mitrano, Matteo; Rak, Melinda S.

One of the most fundamental properties of an interacting electron system is its frequency- and wave-vector-dependent density response function, χ(q,ω). The imaginary part, χ"(q,ω), defines the fundamental bosonic charge excitations of the system, exhibiting peaks wherever collective modes are present. χ quantifies the electronic compressibility of a material, its response to external fields, its ability to screen charge, and its tendency to form charge density waves. Unfortunately, there has never been a fully momentum-resolved means to measure χ(q,ω) at the meV energy scale relevant to modern electronic materials. Here, we demonstrate a way to measure χ with quantitative momentum resolutionmore » by applying alignment techniques from x-ray and neutron scattering to surface high-resolution electron energy-loss spectroscopy (HR-EELS). This approach, which we refer to here as M-EELS" allows direct measurement of χ"(q,ω) with meV resolution while controlling the momentum with an accuracy better than a percent of a typical Brillouin zone. We apply this technique to finite-{\\bf q} excitations in the optimally-doped high temperature superconductor, Bi 2Sr 2CaCu 2O 8+x (Bi2212), which exhibits several phonons potentially relevant to dispersion anomalies observed in ARPES and STM experiments. In conclusion, our study defines a path to studying the long-sought collective charge modes in quantum materials at the meV scale and with full momentum control.« less

Measurement of the dynamic charge response of materials using low-energy, momentum-resolved electron energy-loss spectroscopy (M-EELS)

DOE PAGES

Husain, Ali A.; Mitrano, Matteo; Rak, Melinda S.; ...

2017-10-06

One of the most fundamental properties of an interacting electron system is its frequency- and wave-vector-dependent density response function, χ(q,ω). The imaginary part, χ"(q,ω), defines the fundamental bosonic charge excitations of the system, exhibiting peaks wherever collective modes are present. χ quantifies the electronic compressibility of a material, its response to external fields, its ability to screen charge, and its tendency to form charge density waves. Unfortunately, there has never been a fully momentum-resolved means to measure χ(q,ω) at the meV energy scale relevant to modern electronic materials. Here, we demonstrate a way to measure χ with quantitative momentum resolutionmore » by applying alignment techniques from x-ray and neutron scattering to surface high-resolution electron energy-loss spectroscopy (HR-EELS). This approach, which we refer to here as M-EELS" allows direct measurement of χ"(q,ω) with meV resolution while controlling the momentum with an accuracy better than a percent of a typical Brillouin zone. We apply this technique to finite-{\\bf q} excitations in the optimally-doped high temperature superconductor, Bi 2Sr 2CaCu 2O 8+x (Bi2212), which exhibits several phonons potentially relevant to dispersion anomalies observed in ARPES and STM experiments. In conclusion, our study defines a path to studying the long-sought collective charge modes in quantum materials at the meV scale and with full momentum control.« less

Interpretation of monoclinic hafnia valence electron energy-loss spectra by time-dependent density functional theory

NASA Astrophysics Data System (ADS)

Hung, L.; Guedj, C.; Bernier, N.; Blaise, P.; Olevano, V.; Sottile, F.

2016-04-01

We present the valence electron energy-loss spectrum and the dielectric function of monoclinic hafnia (m -HfO2) obtained from time-dependent density-functional theory (TDDFT) predictions and compared to energy-filtered spectroscopic imaging measurements in a high-resolution transmission-electron microscope. Fermi's golden rule density-functional theory (DFT) calculations can capture the qualitative features of the energy-loss spectrum, but we find that TDDFT, which accounts for local-field effects, provides nearly quantitative agreement with experiment. Using the DFT density of states and TDDFT dielectric functions, we characterize the excitations that result in the m -HfO2 energy-loss spectrum. The sole plasmon occurs between 13 and 16 eV, although the peaks ˜28 and above 40 eV are also due to collective excitations. We furthermore elaborate on the first-principles techniques used, their accuracy, and remaining discrepancies among spectra. More specifically, we assess the influence of Hf semicore electrons (5 p and 4 f ) on the energy-loss spectrum, and find that the inclusion of transitions from the 4 f band damps the energy-loss intensity in the region above 13 eV. We study the impact of many-body effects in a DFT framework using the adiabatic local-density approximation (ALDA) exchange-correlation kernel, as well as from a many-body perspective using "scissors operators" matched to an ab initio G W calculation to account for self-energy corrections. These results demonstrate some cancellation of errors between self-energy and excitonic effects, even for excitations from the Hf 4 f shell. We also simulate the dispersion with increasing momentum transfer for plasmon and collective excitation peaks.

Excitation of phonons in medium-energy electron diffraction

NASA Astrophysics Data System (ADS)

Alvarez, M. A. Vicente; Ascolani, H.; Zampieri, G.

1996-03-01

The ``elastic'' backscattering of electrons from crystalline surfaces presents two regimes: a low-energy regime, in which the characteristic low-energy electron diffraction (LEED) pattern is observed, and a medium-energy regime, in which the diffraction pattern is similar to those observed in x-ray photoemission diffraction (XPD) and Auger electron diffraction (AED) experiments. We present a model for the electron scattering which, including the vibrational degrees of freedom of the crystal, contains both regimes and explains the passage from one regime to the other. Our model is based on a separation of the electron and atomic motions (adiabatic approximation) and on a cluster-type formulation of the multiple scattering of the electron. The inelastic scattering events (excitation and/or absorption of phonons) are treated as coherent processes and no break of the phase relation between the incident and the exit paths of the electron is assumed. The LEED and the medium-energy electron diffraction regimes appear naturally in this model as the limit cases of completely elastic scattering and of inelastic scattering with excitation and/or absorption of multiple phonons. Intensity patterns calculated with this model are in very good agreement with recent experiments of electron scattering on Cu(001) at low and medium energies. We show that there is a correspondence between the type of intensity pattern and the mean number of phonons excited and/or absorbed during the scattering: a LEED-like pattern is observed when this mean number is less than 2, LEED-like and XPD/AED-like features coexist when this number is 3-4, and a XPD/AED-like pattern is observed when this number is greater than 5-6.

Energy gap law of electron transfer in nonpolar solvents.

PubMed

Tachiya, M; Seki, Kazuhiko

2007-09-27

We investigate the energy gap law of electron transfer in nonpolar solvents for charge separation and charge recombination reactions. In polar solvents, the reaction coordinate is given in terms of the electrostatic potentials from solvent permanent dipoles at solutes. In nonpolar solvents, the energy fluctuation due to solvent polarization is absent, but the energy of the ion pair state changes significantly with the distance between the ions as a result of the unscreened strong Coulomb potential. The electron transfer occurs when the final state energy coincides with the initial state energy. For charge separation reactions, the initial state is a neutral pair state, and its energy changes little with the distance between the reactants, whereas the final state is an ion pair state and its energy changes significantly with the mutual distance; for charge recombination reactions, vice versa. We show that the energy gap law of electron-transfer rates in nonpolar solvents significantly depends on the type of electron transfer.

Energy spectra variations of high energy electrons in magnetic storms observed by ARASE and HIMAWARI

NASA Astrophysics Data System (ADS)

Takashima, T.; Higashio, N.; Mitani, T.; Nagatsuma, T.; Yoshizumi, M.

2017-12-01

The ARASE spacecraft was launched in December 20, 2016 to investigate mechanisms for acceleration and loss of relativistic electrons in the radiation belts during space storms. The six particle instruments with wide energy range (a few eV to 10MeV) are onboard the ARASE spacecraft. Especially, two particle instruments, HEP and XEP observe high energy electron with energy range from 70keV to over 10Mev. Those instruments observed several geomagnetic storms caused by coronal hole high speed streams or coronal mass ejections from March in 2017. The relativistic electrons in the outer radiation belt were disappeared/increased and their energy spectra were changed dynamically in some storms observed by XEP/HEP onboard the ARASE spacecraft. In the same time, SEDA-e with energy range 200keV-4.5MeV for electron on board the HIMAWARI-8, Japanese weather satellite on GEO, observed increase of relativistic electron in different local time. We will report on energy spectra variations of high energy electrons including calibrations of differential flux between XEP and HEP and discuss comparisons with energy spectra between ARAE and HIMAWARI that observed each storm in different local time.

Quantum mechanical electronic structure calculation reveals orientation dependence of hydrogen bond energy in proteins.

PubMed

Mondal, Abhisek; Datta, Saumen

2017-06-01

Hydrogen bond plays a unique role in governing macromolecular interactions with exquisite specificity. These interactions govern the fundamental biological processes like protein folding, enzymatic catalysis, molecular recognition. Despite extensive research work, till date there is no proper report available about the hydrogen bond's energy surface with respect to its geometric parameters, directly derived from proteins. Herein, we have deciphered the potential energy landscape of hydrogen bond directly from the macromolecular coordinates obtained from Protein Data Bank using quantum mechanical electronic structure calculations. The findings unravel the hydrogen bonding energies of proteins in parametric space. These data can be used to understand the energies of such directional interactions involved in biological molecules. Quantitative characterization has also been performed using Shannon entropic calculations for atoms participating in hydrogen bond. Collectively, our results constitute an improved way of understanding hydrogen bond energies in case of proteins and complement the knowledge-based potential. Proteins 2017; 85:1046-1055. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Measurement of Trace Constituents by Electron-Excited X-Ray Microanalysis with Energy-Dispersive Spectrometry.

PubMed

Newbury, Dale E; Ritchie, Nicholas W M

2016-06-01

Electron-excited X-ray microanalysis performed with scanning electron microscopy and energy-dispersive spectrometry (EDS) has been used to measure trace elemental constituents of complex multielement materials, where "trace" refers to constituents present at concentrations below 0.01 (mass fraction). High count spectra measured with silicon drift detector EDS were quantified using the standards/matrix correction protocol embedded in the NIST DTSA-II software engine. Robust quantitative analytical results for trace constituents were obtained from concentrations as low as 0.000500 (mass fraction), even in the presence of significant peak interferences from minor (concentration 0.01≤C≤0.1) and major (C>0.1) constituents. Limits of detection as low as 0.000200 were achieved in the absence of peak interference.

Microsecond Electron Beam Source with Electron Energy Up to 400 Kev and Plasma Anode

NASA Astrophysics Data System (ADS)

Abdullin, É. N.; Basov, G. F.; Shershnev, S.

2017-12-01

A new high-power source of electrons with plasma anode for producing high-current microsecond electron beams with electron energy up to 400 keV has been developed, manufactured, and put in operation. To increase the cross section and pulse current duration of the beam, a multipoint explosive emission cathode is used in the electron beam source, and the beam is formed in an applied external guiding magnetic field. The Marx generator with vacuum insulation is used as a high-voltage source. Electron beams with electron energy up to 300-400 keV, current of 5-15 kA, duration of 1.5-3 μs, energy up to 4 kJ, and cross section up to 150 cm2 have been produced. The operating modes of the electron beam source are realized in which the applied voltage is influenced weakly on the current. The possibility of source application for melting of metal surfaces is demonstrated.

Electron emission from surfaces resulting from low energy positron bombardment

NASA Astrophysics Data System (ADS)

Mukherjee, Saurabh

Measurements of the secondary electron energy spectra resulting from very low energy positron bombardment of a polycrystalline Au and Cu (100) surfaces are presented that provide evidence for a single step transition from an unbound scattering state to an image potential bound state. The primary positron energy threshold for secondary electron emission and energy cutoff of the positron induced secondary electron energy peak are consistent with an Auger like process in which an incident positron make a transition from a scattering state to a surface-image potential bound while transferring all of the energy difference to an outgoing secondary electron. We term this process: the Auger mediated quantum sticking effect (AQSE). The intensities of the positron induced secondary electron peak are used to estimate the probability of this process as a function of incident positron energy. Positron annihilation induced Auger spectra (PAES) of Cu and Au are presented that are free of all primary beam induced secondary electron background. This background was eliminated by setting the positron beam energy below AQSE threshold. The background free PAES spectra obtained include the first measurements of the low energy tail of CVV Auger transitions all the way down to zero kinetic energy. The integrated intensity of this tail is several times larger than Auger peak itself which provides strong evidence for multi-electron Auger processes.

Trajectories of high energy electrons in a plasma focus

NASA Technical Reports Server (NTRS)

Harries, W. L.; Lee, J. H.; Mcfarland, D. R.

1978-01-01

Measurements are made of high-energy electron trajectories in a plasma focus as functions of position, time, energy, and angle of emission. The spatial resolution of the X-ray emission shows that low-energy X-rays are emitted from the anode surface. It is also suggested that the highest energy X-rays originate from a small region on the axis. The so-called shadow technique shows that the electron beam is perpendicular to the anode surface. Polar diagrams of medium and high-energy X-rays agree with the bremsstrahlung emission from a relativistic electron beam, the current of which is several 100 A.

Energy-filtered real- and k-space secondary and energy-loss electron imaging with Dual Emission Electron spectro-Microscope: Cs/Mo(110).

PubMed

Grzelakowski, Krzysztof P

2016-05-01

Since its introduction the importance of complementary k||-space (LEED) and real space (LEEM) information in the investigation of surface science phenomena has been widely demonstrated over the last five decades. In this paper we report the application of a novel kind of electron spectromicroscope Dual Emission Electron spectroMicroscope (DEEM) with two independent electron optical channels for reciprocal and real space quasi-simultaneous imaging in investigation of a Cs covered Mo(110) single crystal by using the 800eV electron beam from an "in-lens" electron gun system developed for the sample illumination. With the DEEM spectromicroscope it is possible to observe dynamic, irreversible processes at surfaces in the energy-filtered real space and in the corresponding energy-filtered kǁ-space quasi-simultaneously in two independent imaging columns. The novel concept of the high energy electron beam sample illumination in the cathode lens based microscopes allows chemically selective imaging and analysis under laboratory conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

Electron energy recovery system for negative ion sources

DOEpatents

Dagenhart, William K.; Stirling, William L.

1982-01-01

An electron energy recovery system for negative ion sources is provided. The system, employs crossed electric and magnetic fields to separate the electrons from ions as they are extracted from a negative ion source plasma generator and before the ions are accelerated to their full kinetic energy. With the electric and magnetic fields oriented 90.degree. to each other, the electrons are separated from the plasma and remain at approximately the electrical potential of the generator in which they were generated. The electrons migrate from the ion beam path in a precessing motion out of the ion accelerating field region into an electron recovery region provided by a specially designed electron collector electrode. The electron collector electrode is uniformly spaced from a surface of the ion generator which is transverse to the direction of migration of the electrons and the two surfaces are contoured in a matching relationship which departs from a planar configuration to provide an electric field component in the recovery region which is parallel to the magnetic field thereby forcing the electrons to be directed into and collected by the electron collector electrode. The collector electrode is maintained at a potential slightly positive with respect to the ion generator so that the electrons are collected at a small fraction of the full accelerating supply voltage energy.

Energy-Filtered Tunnel Transistor: A New Device Concept Toward Extremely-Low Energy Consumption Electronics

DTIC Science & Technology

2015-12-17

temperature . New device architecture that utilizes cold-electron transport for ultra-low energy consumption electronics has been designed in a configuration...the oxygen has also been found important for the SiC>2 sputter deposition. The sputter was carried out at room temperature . Our optimized process...have been pursued for two electronic devices, 1) room- temperature single-electron transistors, and 2) ultralow energy consumption transistors. For

Geometries and focal properties of two electron-lens systems useful in low-energy electron or ion scattering

NASA Technical Reports Server (NTRS)

Chutjian, A.

1979-01-01

Geometries and focal properties are given for two types of electron-lens system commonly needed in electron scattering. One is an electron gun that focuses electrons from a thermionic emitter onto a fixed point (target) over a wide range of final energies. The other is an electron analyzer system that focuses scattered electrons of variable energy onto a fixed position (e.g., the entrance plane of an analyzer) at fixed energy with a zero final beam angle. Analyzer-system focusing properties are given for superelastically, elastically, and inelastically scattered electrons. Computer calculations incorporating recent accurate tube-lens focal properties are used to compute lens voltages, locations and diameters of all pupils and windows, filling factors, and asymptotic rays throughout each lens system. Focus voltages as a function of electron energy and energy change are given, and limits of operation of each system discussed. Both lens systems have been in routine use for several years, and good agreement has been consistently found between calculated and operating lens voltages.

Ultra high energy electrons powered by pulsar rotation.

PubMed

Mahajan, Swadesh; Machabeli, George; Osmanov, Zaza; Chkheidze, Nino

2013-01-01

A new mechanism of particle acceleration, driven by the rotational slow down of the Crab pulsar, is explored. The rotation, through the time dependent centrifugal force, can efficiently excite unstable Langmuir waves in the electron-positron (hereafter e(±)) plasma of the star magnetosphere. These waves, then, Landau damp on electrons accelerating them in the process. The net transfer of energy is optimal when the wave growth and the Landau damping times are comparable and are both very short compared to the star rotation time. We show, by detailed calculations, that these are precisely the conditions for the parameters of the Crab pulsar. This highly efficient route for energy transfer allows the electrons in the primary beam to be catapulted to multiple TeV (~ 100 TeV) and even PeV energy domain. It is expected that the proposed mechanism may, unravel the puzzle of the origin of ultra high energy cosmic ray electrons.

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

The source of multi spectral energy of solar energetic electron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herdiwijaya, Dhani

2015-04-16

We study the solar energetic electron distribution obtained from ACE and GOES satellites which have different altitudes and electron spectral energy during the year 1997 to 2011. The electron spectral energies were 0.038–0.315 MeV from EPAM instrument onboard ACE satellite and >2 MeV from GOES satellite. We found that the low electron energy has no correlation with high energy. In spite of we have corrected to the altitude differences. It implied that they originated from time dependent events with different sources and physical processes at the solar atmosphere. The sources of multi spectral energetic electron were related to flare andmore » CME phenomena. However, we also found that high energetic electron comes from coronal hole.« less

Characteristic energy range of electron scattering due to plasmaspheric hiss

DOE PAGES

Ma, Q.; Li, W.; Thorne, R. M.; ...

2016-11-15

In this paper, we investigate the characteristic energy range of electron flux decay due to the interaction with plasmaspheric hiss in the Earth's inner magnetosphere. The Van Allen Probes have measured the energetic electron flux decay profiles in the Earth's outer radiation belt during a quiet period following the geomagnetic storm that occurred on 7 November 2015. The observed energy of significant electron decay increases with decreasing L shell and is well correlated with the energy band corresponding to the first adiabatic invariant μ = 4–200 MeV/G. The electron diffusion coefficients due to hiss scattering are calculated at L =more » 2–6, and the modeled energy band of effective pitch angle scattering is also well correlated with the constant μ lines and is consistent with the observed energy range of electron decay. Using the previously developed statistical plasmaspheric hiss model during modestly disturbed periods, we perform a 2-D Fokker-Planck simulation of the electron phase space density evolution at L = 3.5 and demonstrate that plasmaspheric hiss causes the significant decay of 100 keV–1 MeV electrons with the largest decay rate occurring at around 340 keV, forming anisotropic pitch angle distributions at lower energies and more flattened distributions at higher energies. Finally, our study provides reasonable estimates of the electron populations that can be most significantly affected by plasmaspheric hiss and the consequent electron decay profiles.« less

Quantitative Assessment of CRAND Contribution to the Inner Belt Electron Intensity

NASA Astrophysics Data System (ADS)

Zhang, K.; Li, X.; Selesnick, R.; Schiller, Q. A.; Zhao, H.; Baker, D. N.; Temerin, M. A.

2017-12-01

Following the direct identification and measurements of Cosmic Ray Albedo Neutron Decay (CRAND) produced electrons near the inner edge of the inner belt by Colorado Student Space Weather Experiment (CSSWE)1, we extend the study by addressing more comprehensive questions: (1) what is the relative CRAND contribution to the inner belt compared with electrons injected from further out? (2) How does this relative contribution vary with geomagnetic activity and electron energy? (3) What is the solar cycle dependence of CRAND electrons? In order to answer the above questions, extended data of relativistic electrons in the inner belt are needed for a much longer time period and also finer energy resolution is required. Therefore, we will show results regarding the above questions based on data including other low Earth orbit measurements in addition to CSSWE, such as SAMPEX/PET, DEMETER/IDP, and PROBA-V/EPT. [1] Li, Xinlin, Richard Selesnick, Quintin Schiller, Kun Zhang, Hong Zhao, Daniel Baker, and Michael Temerin (2017), Direct detection of albedo neutron decay electrons at the inner edge of the radiation belt and determination of neutron density in near-Earth space, Nature, under review.

Diffusion of low-energy electrons in tissue-like liquids.

PubMed

Malamut, C; Paes-Leme, P J; Paschoa, A S

1992-11-01

The spatial-energetic distribution of low-energy electrons was studied for a source located in a liquid medium simulating biological tissue. A time-independent Boltzmann equation was used to model this distribution microscopically. Ionization was treated as a perturbation to a quasi-elastic collision process between the electron and the medium. A diffusion limit was obtained by using a scale parameter, leading to a sequence of recursive partial differential equations whose solutions, associated with a macroscopic scale, were obtained by numerical approximations. As an application, electron ranges were estimated based on these solutions and then compared with values reported in the open literature based on experimental results and on Monte Carlo calculation. Local dosimetry, i.e., the energy imparted to a volume of a sphere with radius equal to the range of low-energy electrons, of low-energy electrons from internal emitters can benefit by the knowledge of the ranges estimated for biological tissue. Auger electron emitters, for example, have been the object of a number of investigations because of their radiobiological significance.

Hot-electron-based solar energy conversion with metal-semiconductor nanodiodes.

PubMed

Lee, Young Keun; Lee, Hyosun; Lee, Changhwan; Hwang, Euyheon; Park, Jeong Young

2016-06-29

Energy dissipation at metal surfaces or interfaces between a metal and a dielectric generally results from elementary excitations, including phonons and electronic excitation, once external energy is deposited to the surface/interface during exothermic chemical processes or an electromagnetic wave incident. In this paper, we outline recent research activities to develop energy conversion devices based on hot electrons. We found that photon energy can be directly converted to hot electrons and that hot electrons flow through the interface of metal-semiconductor nanodiodes where a Schottky barrier is formed and the energy barrier is much lower than the work function of the metal. The detection of hot electron flow can be successfully measured using the photocurrent; we measured the photoyield of photoemission with incident photons-to-current conversion efficiency (IPCE). We also show that surface plasmons (i.e. the collective oscillation of conduction band electrons induced by interaction with an electromagnetic field) are excited on a rough metal surface and subsequently decay into secondary electrons, which gives rise to enhancement of the IPCE. Furthermore, the unique optical behavior of surface plasmons can be coupled with dye molecules, suggesting the possibility for producing additional channels for hot electron generation.

Degradation of vitamin C by low-energy electrons

NASA Astrophysics Data System (ADS)

Abdoul-Carime, Hassan; Illenberger, Eugen

2004-06-01

We report on the degradation of gas phase vitamin C (ascorbic acid, AA) induced by low-energy electrons. In the energy range of (0-12) eV, different negatively charged fragments, attributed to the dehydro-ascorbic acid anion ((AA-H) -), OH -, O - and H -, are observed. The yield functions indicate that these ions are formed via dissociative electron attachment, DEA. While the formation of (AA-H) - is exclusively observed at sub-excitation energies (<1.5 eV), the other fragments arise from resonance features at higher energies. Possible implications of these observations for radiation damage and food treatment by high energy radiation are considered.

Energy-weighted dynamical scattering simulations of electron diffraction modalities in the scanning electron microscope.

PubMed

Pascal, Elena; Singh, Saransh; Callahan, Patrick G; Hourahine, Ben; Trager-Cowan, Carol; Graef, Marc De

2018-04-01

Transmission Kikuchi diffraction (TKD) has been gaining momentum as a high resolution alternative to electron back-scattered diffraction (EBSD), adding to the existing electron diffraction modalities in the scanning electron microscope (SEM). The image simulation of any of these measurement techniques requires an energy dependent diffraction model for which, in turn, knowledge of electron energies and diffraction distances distributions is required. We identify the sample-detector geometry and the effect of inelastic events on the diffracting electron beam as the important factors to be considered when predicting these distributions. However, tractable models taking into account inelastic scattering explicitly are lacking. In this study, we expand the Monte Carlo (MC) energy-weighting dynamical simulations models used for EBSD [1] and ECP [2] to the TKD case. We show that the foil thickness in TKD can be used as a means of energy filtering and compare band sharpness in the different modalities. The current model is shown to correctly predict TKD patterns and, through the dictionary indexing approach, to produce higher quality indexed TKD maps than conventional Hough transform approach, especially close to grain boundaries. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Low energy electron attenuation lengths in core–shell nanoparticles

DOE PAGES

Jacobs, Michael I.; Kostko, Oleg; Ahmed, Musahid; ...

2017-05-05

Here, a velocity map imaging spectrometer is used to measure photoemission from free core–shell nanoparticles, where a salt core is coated with a liquid hydrocarbon shell (i.e. squalane). By varying the radial thickness of the hydrocarbon shell, electron attenuation lengths (EALs) are determined by measuring the decay in photoemission intensity from the salt core. In squalane, electrons with kinetic energy (KE) above 2 eV are found to have EALs of 3–5 nm, whereas electrons with smaller KE (<2 eV) have significantly larger EALs of >15 nm. These results (in the context of other energy-resolved EAL measurements) suggest that the energymore » dependent behavior of low energy electrons is similar in dielectrics when KE > 2 eV. At this energy the EALs do not appear to exhibit strong energy dependence. However, at very low KE (<2 eV), the EALs diverge and appear to be extremely material dependent.« less

Electronic energy transfer through non-adiabatic vibrational-electronic resonance. II. 1D spectra for a dimer.

PubMed

Tiwari, Vivek; Jonas, David M

2018-02-28

Vibrational-electronic resonance in photosynthetic pigment-protein complexes invalidates Förster's adiabatic framework for interpreting spectra and energy transfer, thus complicating determination of how the surrounding protein affects pigment properties. This paper considers the combined effects of vibrational-electronic resonance and inhomogeneous variations in the electronic excitation energies of pigments at different sites on absorption, emission, circular dichroism, and hole-burning spectra for a non-degenerate homodimer. The non-degenerate homodimer has identical pigments in different sites that generate differences in electronic energies, with parameters loosely based on bacteriochlorophyll a pigments in the Fenna-Matthews-Olson antenna protein. To explain the intensity borrowing, the excited state vibrational-electronic eigenvectors are discussed in terms of the vibrational basis localized on the individual pigments, as well as the correlated/anti-correlated vibrational basis delocalized over both pigments. Compared to those in the isolated pigment, vibrational satellites for the correlated vibration have the same frequency and precisely a factor of 2 intensity reduction through vibrational delocalization in both absorption and emission. Vibrational satellites for anti-correlated vibrations have their relaxed emission intensity reduced by over a factor 2 through vibrational and excitonic delocalization. In absorption, anti-correlated vibrational satellites borrow excitonic intensity but can be broadened away by the combination of vibronic resonance and site inhomogeneity; in parallel, their vibronically resonant excitonic partners are also broadened away. These considerations are consistent with photosynthetic antenna hole-burning spectra, where sharp vibrational and excitonic satellites are absent. Vibrational-excitonic resonance barely alters the inhomogeneously broadened linear absorption, emission, and circular dichroism spectra from those for a

Electronic energy transfer through non-adiabatic vibrational-electronic resonance. II. 1D spectra for a dimer

NASA Astrophysics Data System (ADS)

Tiwari, Vivek; Jonas, David M.

2018-02-01

Vibrational-electronic resonance in photosynthetic pigment-protein complexes invalidates Förster's adiabatic framework for interpreting spectra and energy transfer, thus complicating determination of how the surrounding protein affects pigment properties. This paper considers the combined effects of vibrational-electronic resonance and inhomogeneous variations in the electronic excitation energies of pigments at different sites on absorption, emission, circular dichroism, and hole-burning spectra for a non-degenerate homodimer. The non-degenerate homodimer has identical pigments in different sites that generate differences in electronic energies, with parameters loosely based on bacteriochlorophyll a pigments in the Fenna-Matthews-Olson antenna protein. To explain the intensity borrowing, the excited state vibrational-electronic eigenvectors are discussed in terms of the vibrational basis localized on the individual pigments, as well as the correlated/anti-correlated vibrational basis delocalized over both pigments. Compared to those in the isolated pigment, vibrational satellites for the correlated vibration have the same frequency and precisely a factor of 2 intensity reduction through vibrational delocalization in both absorption and emission. Vibrational satellites for anti-correlated vibrations have their relaxed emission intensity reduced by over a factor 2 through vibrational and excitonic delocalization. In absorption, anti-correlated vibrational satellites borrow excitonic intensity but can be broadened away by the combination of vibronic resonance and site inhomogeneity; in parallel, their vibronically resonant excitonic partners are also broadened away. These considerations are consistent with photosynthetic antenna hole-burning spectra, where sharp vibrational and excitonic satellites are absent. Vibrational-excitonic resonance barely alters the inhomogeneously broadened linear absorption, emission, and circular dichroism spectra from those for a

Quantitative Detection of Trace Explosive Vapors by Programmed Temperature Desorption Gas Chromatography-Electron Capture Detector

PubMed Central

Field, Christopher R.; Lubrano, Adam; Woytowitz, Morgan; Giordano, Braden C.; Rose-Pehrsson, Susan L.

2014-01-01

The direct liquid deposition of solution standards onto sorbent-filled thermal desorption tubes is used for the quantitative analysis of trace explosive vapor samples. The direct liquid deposition method yields a higher fidelity between the analysis of vapor samples and the analysis of solution standards than using separate injection methods for vapors and solutions, i.e., samples collected on vapor collection tubes and standards prepared in solution vials. Additionally, the method can account for instrumentation losses, which makes it ideal for minimizing variability and quantitative trace chemical detection. Gas chromatography with an electron capture detector is an instrumentation configuration sensitive to nitro-energetics, such as TNT and RDX, due to their relatively high electron affinity. However, vapor quantitation of these compounds is difficult without viable vapor standards. Thus, we eliminate the requirement for vapor standards by combining the sensitivity of the instrumentation with a direct liquid deposition protocol to analyze trace explosive vapor samples. PMID:25145416

Quantitative detection of trace explosive vapors by programmed temperature desorption gas chromatography-electron capture detector.

PubMed

Field, Christopher R; Lubrano, Adam; Woytowitz, Morgan; Giordano, Braden C; Rose-Pehrsson, Susan L

2014-07-25

The direct liquid deposition of solution standards onto sorbent-filled thermal desorption tubes is used for the quantitative analysis of trace explosive vapor samples. The direct liquid deposition method yields a higher fidelity between the analysis of vapor samples and the analysis of solution standards than using separate injection methods for vapors and solutions, i.e., samples collected on vapor collection tubes and standards prepared in solution vials. Additionally, the method can account for instrumentation losses, which makes it ideal for minimizing variability and quantitative trace chemical detection. Gas chromatography with an electron capture detector is an instrumentation configuration sensitive to nitro-energetics, such as TNT and RDX, due to their relatively high electron affinity. However, vapor quantitation of these compounds is difficult without viable vapor standards. Thus, we eliminate the requirement for vapor standards by combining the sensitivity of the instrumentation with a direct liquid deposition protocol to analyze trace explosive vapor samples.

Electronic Delocalization, Vibrational Dynamics and Energy Transfer in Organic Chromophores

DOE PAGES

Nelson, Tammie Renee; Fernandez Alberti, Sebastian; Roitberg, Adrian; ...

2017-06-12

The efficiency of materials developed for solar energy and technological applications depends on the interplay between molecular architecture and light-induced electronic energy redistribution. The spatial localization of electronic excitations is very sensitive to molecular distortions. Vibrational nuclear motions can couple to electronic dynamics driving changes in localization. The electronic energy transfer among multiple chromophores arises from several distinct mechanisms that can give rise to experimentally measured signals. Atomistic simulations of coupled electron-vibrational dynamics can help uncover the nuclear motions directing energy flow. Through careful analysis of excited state wave function evolution and a useful fragmenting of multichromophore systems, through-bond transportmore » and exciton hopping (through-space) mechanisms can be distinguished. Such insights are crucial in the interpretation of fluorescence anisotropy measurements and can aid materials design. Finally, this Perspective highlights the interconnected vibrational and electronic motions at the foundation of nonadiabatic dynamics where nuclear motions, including torsional rotations and bond vibrations, drive electronic transitions.« less

The uniformity study of non-oxide thin film at device level using electron energy loss spectroscopy

NASA Astrophysics Data System (ADS)

Li, Zhi-Peng; Zheng, Yuankai; Li, Shaoping; Wang, Haifeng

2018-05-01

Electron energy loss spectroscopy (EELS) has been widely used as a chemical analysis technique to characterize materials chemical properties, such as element valence states, atoms/ions bonding environment. This study provides a new method to characterize physical properties (i.e., film uniformity, grain orientations) of non-oxide thin films in the magnetic device by using EELS microanalysis on scanning transmission electron microscope. This method is based on analyzing white line ratio of spectra and related extended energy loss fine structures so as to correlate it with thin film uniformity. This new approach can provide an effective and sensitive method to monitor/characterize thin film quality (i.e., uniformity) at atomic level for thin film development, which is especially useful for examining ultra-thin films (i.e., several nanometers) or embedded films in devices for industry applications. More importantly, this technique enables development of quantitative characterization of thin film uniformity and it would be a remarkably useful technique for examining various types of devices for industrial applications.

The energy spectrum of Jovian electrons in interplanetary space

NASA Technical Reports Server (NTRS)

Christon, S. P.; Cummings, A. C.; Stone, E. C.; Webber, W. R.

1985-01-01

The energy spectrum of electrons with energies approximately 10 to approximately 180 MeV measured with the electron telescope on the Voyager 1 and 2 spacecraft in interplanetary space from 1978 to 1983 is reported. The kinetic energy of electrons is determined by double dE/dx measurements from the first two detectors (D1,D2) of a stack of eight solid state detectors and by the range of particle penetration into the remaining six detectors (D3 to D8) which are interleaved with tungsten absorbers.

Dielectric surface discharges: Effects of combined low-energy and high-energy incident electrons

NASA Technical Reports Server (NTRS)

Balmain, K. G.; Hirt, W.

1981-01-01

Dielectric surface discharges affected by the addition of high energy electrons at 5 pA/sq cm to a primary 20 keV, 10 nA/sq cm electron beam with the high energy broad spectrum particles coming from the beta decay of Strontium 90 are studied. Kapton exhibits significantly increased discharge strength, increased waiting time between discharges, and a decreased number of discharges per specimen before discharge cessation. Mylar exhibits similar but less pronounced effects, while Teflon is relatively unaffected. With Kapton and Mylar, the high energy electrons act in some way to delay the instant of discharge ignition so that more charge can be accumulated and hence released during discharge.

Low Energy Electrons in the Mars Plasma Environment

NASA Technical Reports Server (NTRS)

Link, Richard

2001-01-01

The ionosphere of Mars is rather poorly understood. The only direct measurements were performed by the Viking 1 and 2 landers in 1976, both of which carried a Retarding Potential Analyzer. The RPA was designed to measure ion properties during the descent, although electron fluxes were estimated from changes in the ion currents. Using these derived low-energy electron fluxes, Mantas and Hanson studied the photoelectron and the solar wind electron interactions with the atmosphere and ionosphere of Mars. Unanswered questions remain regarding the origin of the low-energy electron fluxes in the vicinity of the Mars plasma boundary. Crider, in an analysis of Mars Global Surveyor Magnetometer/Electron Reflectometer measurements, has attributed the formation of the magnetic pile-up boundary to electron impact ionization of exospheric neutral species by solar wind electrons. However, the role of photoelectrons escaping from the lower ionosphere was not determined. In the proposed work, we will examine the role of solar wind and ionospheric photoelectrons in producing ionization in the upper ionosphere of Mars. Low-energy (< 4 keV) electrons will be modeled using the two-stream electron transport code of Link. The code models both external (solar wind) and internal (photoelectron) sources of ionization, and accounts for Auger electron production. The code will be used to analyze Mars Global Surveyor measurements of solar wind and photoelectrons down to altitudes below 200 km in the Mars ionosphere, in order to determine the relative roles of solar wind and escaping photoelectrons in maintaining plasma densities in the region of the Mars plasma boundary.

Experimental observation of electron bounce resonance through electron energy distribution measurement in a finite size inductively coupled plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gu, Seuli; Kang, Hyun-Ju; Kim, Yu-Sin

2016-06-15

The electron bounce resonance was experimentally investigated in a low pressure planar inductively coupled plasma. The electron energy probability functions (EEPFs) were measured at different chamber heights and the energy diffusion coefficients were calculated by the kinetic model. It is found that the EEPFs begin to flatten at the first electron bounce resonance condition, and the plateau shifts to a higher electron energy as the chamber height increases. The plateau which indicates strong electron heating corresponds not only to the electron bounce resonance condition but also to the peaks of the first component of the energy diffusion coefficients. As amore » result, the plateau formation in the EEPFs is mainly due to the electron bounce resonance in a finite inductive discharge.« less

Improving Short Term Instability for Quantitative Analyses with Portable Electronic Noses

PubMed Central

Macías, Miguel Macías; Agudo, J. Enrique; Manso, Antonio García; Orellana, Carlos Javier García; Velasco, Horacio Manuel González; Caballero, Ramón Gallardo

2014-01-01

One of the main problems when working with electronic noses is the lack of reproducibility or repeatability of the sensor response, so that, if this problem is not properly considered, electronic noses can be useless, especially for quantitative analyses. On the other hand, irreproducibility is increased with portable and low cost electronic noses where laboratory equipment like gas zero generators cannot be used. In this work, we study the reproducibility of two portable electronic noses, the PEN3 (commercial) and CAPINose (a proprietary design) by using synthetic wine samples. We show that in both cases short term instability associated to the sensors' response to the same sample and under the same conditions represents a major problem and we propose an internal normalization technique that, in both cases, reduces the variability of the sensors' response. Finally, we show that the normalization proposed seems to be more effective in the CAPINose case, reducing, for example, the variability associated to the TGS2602 sensor from 12.19% to 2.2%. PMID:24932869

Absolute cross-sections for DNA strand breaks and crosslinks induced by low energy electrons

PubMed Central

Chen, Wenzhuang; Chen, Shiliang; Dong, Yanfang; Cloutier, Pierre; Sanche, Léon

2016-01-01

Absolute cross sections (CSs) for the interaction of low energy electrons with condensed macromolecules are essential parameters to accurately model ionizing radiation induced reactions. To determine CSs for various conformational DNA damage induced by 2–20 eV electrons, we investigated the influence of the attenuation length (AL) and penetration factor (f) using a mathematical model. Solid films of super-coiled plasmid DNA with thicknesses of 10, 15 and 20 nm were irradiated with 4.6, 5.6, 9.6 and 14.6 eV electrons. DNA conformational changes were quantified by gel electrophoresis, and the respective yields were extrapolated from exposure–response curves. The absolute CS, AL and f values were generated by applying the model developed by Rezaee et al. The values of AL were found to lie between 11 and 16 nm with the maximum at 14.6 eV. The absolute CSs for the loss of the supercoiled (LS) configuration and production of crosslinks (CL), single strand breaks (SSB) and double strand breaks (DSB) induced by 4.6, 5.6, 9.6 and 14.6 eV electrons are obtained. The CSs for SSB are smaller, but similar to those for LS, indicating that SSB are the main conformational damage. The CSs for DSB and CL are about one order of magnitude smaller than those of LS and SSB. The value of f is found to be independent of electron energy, which allows extending the absolute CSs for these types of damage within the range 2–20 eV, from previous measurements of effective CSs. When comparison is possible, the absolute CSs are found to be in good agreement with those obtained from previous similar studies with double-stranded DNA. The high values of the absolute CSs of 4.6 and 9.6 eV provide quantitative evidence for the high efficiency of low energy electrons to induce DNA damage via the formation of transient anions. PMID:27878170

Absolute cross-sections for DNA strand breaks and crosslinks induced by low energy electrons.

PubMed

Chen, Wenzhuang; Chen, Shiliang; Dong, Yanfang; Cloutier, Pierre; Zheng, Yi; Sanche, Léon

2016-12-07

Absolute cross sections (CSs) for the interaction of low energy electrons with condensed macromolecules are essential parameters to accurately model ionizing radiation induced reactions. To determine CSs for various conformational DNA damage induced by 2-20 eV electrons, we investigated the influence of the attenuation length (AL) and penetration factor (f) using a mathematical model. Solid films of supercoiled plasmid DNA with thicknesses of 10, 15 and 20 nm were irradiated with 4.6, 5.6, 9.6 and 14.6 eV electrons. DNA conformational changes were quantified by gel electrophoresis, and the respective yields were extrapolated from exposure-response curves. The absolute CS, AL and f values were generated by applying the model developed by Rezaee et al. The values of AL were found to lie between 11 and 16 nm with the maximum at 14.6 eV. The absolute CSs for the loss of the supercoiled (LS) configuration and production of crosslinks (CL), single strand breaks (SSB) and double strand breaks (DSB) induced by 4.6, 5.6, 9.6 and 14.6 eV electrons are obtained. The CSs for SSB are smaller, but similar to those for LS, indicating that SSB are the main conformational damage. The CSs for DSB and CL are about one order of magnitude smaller than those of LS and SSB. The value of f is found to be independent of electron energy, which allows extending the absolute CSs for these types of damage within the range 2-20 eV, from previous measurements of effective CSs. When comparison is possible, the absolute CSs are found to be in good agreement with those obtained from previous similar studies with double-stranded DNA. The high values of the absolute CSs of 4.6 and 9.6 eV provide quantitative evidence for the high efficiency of low energy electrons to induce DNA damage via the formation of transient anions.

Kinetic energy offsets for multicharged ions from an electron beam ion source.

PubMed

Kulkarni, D D; Ahl, C D; Shore, A M; Miller, A J; Harriss, J E; Sosolik, C E; Marler, J P

2017-08-01

Using a retarding field analyzer, we have measured offsets between the nominal and measured kinetic energy of multicharged ions extracted from an electron beam ion source (EBIS). By varying source parameters, a shift in ion kinetic energy was attributed to the trapping potential produced by the space charge of the electron beam within the EBIS. The space charge of the electron beam depends on its charge density, which in turn depends on the amount of negative charge (electron beam current) and its velocity (electron beam energy). The electron beam current and electron beam energy were both varied to obtain electron beams of varying space charge and these were related to the observed kinetic energy offsets for Ar 4+ and Ar 8+ ion beams. Knowledge of these offsets is important for studies that seek to utilize slow, i.e., low kinetic energy, multicharged ions to exploit their high potential energies for processes such as surface modification. In addition, we show that these offsets can be utilized to estimate the effective radius of the electron beam inside the trap.

Electron Identification and Energy Measurement with Emulsion Cloud Chamber

NASA Astrophysics Data System (ADS)

Kitagawa, Nobuko; Komatsu, Masahiro

Charged particles undergo the Multiple Coulomb Scattering (MCS) when passing through a material. Their momentum can be estimated from the distribution of the scattering angle directly. Angle of electrons (or positrons) largely changes because of the energy loss in bremsstrahlung, and they are distinguished from other charged particles by making use of its feature. Electron energy is generally measured by counting of electromagnetic shower (e.m. shower) tracks in Emulsion Cloud Chamber (ECC), so enough absorber material is needed to develop the shower. In the range from sub-GeV to a few GeV, electrons don't develop noticeable showers. In order to estimate the energy of electrons in this range with a limited material, we established the new method which is based on the scattering angle considering the energy loss in bremsstrahlung. From the Monte Carlo simulation (MC) data, which is generated by electron beam (0.5 GeV, 1 GeV, 2 GeV) exposure to ECC, we derived the correlation between energy and scattering angle in each emulsion layer. We fixed the function and some parameters which 1 GeV MC sample would return 1 GeV as the center value, and then applied to 0.5 GeV and 2 GeV sample and confirmed the energy resolution about 50% within two radiation length.

Shape and energy consistent pseudopotentials for correlated electron systems

PubMed Central

Needs, R. J.

2017-01-01

A method is developed for generating pseudopotentials for use in correlated-electron calculations. The paradigms of shape and energy consistency are combined and defined in terms of correlated-electron wave-functions. The resulting energy consistent correlated electron pseudopotentials (eCEPPs) are constructed for H, Li–F, Sc–Fe, and Cu. Their accuracy is quantified by comparing the relaxed molecular geometries and dissociation energies which they provide with all electron results, with all quantities evaluated using coupled cluster singles, doubles, and triples calculations. Errors inherent in the pseudopotentials are also compared with those arising from a number of approximations commonly used with pseudopotentials. The eCEPPs provide a significant improvement in optimised geometries and dissociation energies for small molecules, with errors for the latter being an order-of-magnitude smaller than for Hartree-Fock-based pseudopotentials available in the literature. Gaussian basis sets are optimised for use with these pseudopotentials. PMID:28571391

The EIGER detector for low-energy electron microscopy and photoemission electron microscopy.

PubMed

Tinti, G; Marchetto, H; Vaz, C A F; Kleibert, A; Andrä, M; Barten, R; Bergamaschi, A; Brückner, M; Cartier, S; Dinapoli, R; Franz, T; Fröjdh, E; Greiffenberg, D; Lopez-Cuenca, C; Mezza, D; Mozzanica, A; Nolting, F; Ramilli, M; Redford, S; Ruat, M; Ruder, Ch; Schädler, L; Schmidt, Th; Schmitt, B; Schütz, F; Shi, X; Thattil, D; Vetter, S; Zhang, J

2017-09-01

EIGER is a single-photon-counting hybrid pixel detector developed at the Paul Scherrer Institut, Switzerland. It is designed for applications at synchrotron light sources with photon energies above 5 keV. Features of EIGER include a small pixel size (75 µm × 75 µm), a high frame rate (up to 23 kHz), a small dead-time between frames (down to 3 µs) and a dynamic range up to 32-bit. In this article, the use of EIGER as a detector for electrons in low-energy electron microscopy (LEEM) and photoemission electron microscopy (PEEM) is reported. It is demonstrated that, with only a minimal modification to the sensitive part of the detector, EIGER is able to detect electrons emitted or reflected by the sample and accelerated to 8-20 keV. The imaging capabilities are shown to be superior to the standard microchannel plate detector for these types of applications. This is due to the much higher signal-to-noise ratio, better homogeneity and improved dynamic range. In addition, the operation of the EIGER detector is not affected by radiation damage from electrons in the present energy range and guarantees more stable performance over time. To benchmark the detector capabilities, LEEM experiments are performed on selected surfaces and the magnetic and electronic properties of individual iron nanoparticles with sizes ranging from 8 to 22 nm are detected using the PEEM endstation at the Surface/Interface Microscopy (SIM) beamline of the Swiss Light Source.

Low-energy Electrons in Gamma-Ray Burst Afterglow Models

NASA Astrophysics Data System (ADS)

Jóhannesson, Guđlaugur; Björnsson, Gunnlaugur

2018-05-01

Observations of gamma-ray burst (GRB) afterglows have long provided the most detailed information about the origin of this spectacular phenomenon. The model that is most commonly used to extract physical properties of the event from the observations is the relativistic fireball model, where ejected material moving at relativistic speeds creates a shock wave when it interacts with the surrounding medium. Electrons are accelerated in the shock wave, generating the observed synchrotron emission through interactions with the magnetic field in the downstream medium. It is usually assumed that the accelerated electrons follow a simple power-law distribution in energy between specific energy boundaries, and that no electron exists outside these boundaries. This Letter explores the consequences of adding a low-energy power-law segment to the electron distribution with energy that contributes insignificantly to the total energy budget of the distribution. The low-energy electrons have a significant impact on the radio emission, providing synchrotron absorption and emission at these long wavelengths. Shorter wavelengths are affected through the normalization of the distribution. The new model is used to analyze the light curves of GRB 990510, and the resulting parameters are compared to a model without the extra electrons. The quality of the fit and the best-fit parameters are significantly affected by the additional model component. The new component is in one case found to strongly affect the X-ray light curves, showing how changes to the model at radio frequencies can affect light curves at other frequencies through changes in best-fit model parameters.

Re-Visiting the Electronic Energy Map of the Copper Dimer by Double-Resonant Four-Wave Mixing

NASA Astrophysics Data System (ADS)

Visser, Bradley; Bornhauser, Peter; Beck, Martin; Knopp, Gregor; Marquardt, Roberto; Gourlaouen, Christophe; van Bokhoven, Jeroen A.; Radi, Peter

2017-06-01

The copper dimer is one of the most studied transition metal (TM) diatomics due to its alkali-metal like electronic shell structure, strongly bound ground state and chemical reactivity. The high electronic promotion energy in the copper atom yields numerous low-lying electronic states compared to TM dimers with d)-hole electronic configurations. Thus, through extensive study the excited electronic structure of Cu_2 is relatively well known, however in practice few excited states have been investigated with rotational resolution or even assigned term symbols or dissociation limits. The spectroscopic methods that have been used to investigate the copper dimer until now have not possessed sufficient spectral selectivity, which has complicated the analysis of the often overlapping transitions. Resonant four-wave mixing is a non-linear absorption based spectroscopic method. In favorable cases, the two-color version (TC-RFWM) enables purely optical mass selective spectral measurements in a mixed molecular beam. Additionally, by labelling individual rotational levels in the common intermediate state the spectra are dramatically simplified. In this work, we report on the rotationally resolved characterization of low-lying electronic states of dicopper. Several term symbols have been assigned unambiguously. De-perturbation studies performed shed light on the complex electronic structure of the molecule. Furthermore, a new low-lying electronic state of Cu_2 is discovered and has important implications for the high-level theoretical structure calculations performed in parallel. In fact, the ab initio methods applied yield relative energies among the electronic levels that are almost quantitative and allow assignment of the newly observed state that is governed by spin-orbit interacting levels.

Propagation of low energy solar electrons

NASA Technical Reports Server (NTRS)

Anderson, K. A.; Mcfadden, J. P.; Lin, R. P.

1981-01-01

Two events are reported in which 2-10 keV electrons of solar energy have undergone significant adiabatic mirroring and pitch angle scattering in large scale magnetic structures in the interplanetary medium within a distance of about 0.5 AU from the earth. Electrons of 3 keV, typical of the energies measured, have a speed of about one-tenth of the speed of light, so that their travel time from the sun at 0 deg pitch angle would be about 100 minutes. Their cyclotron radius is about 20 km for a pitch angle of 30 deg, and a field of magnitude of 5 nT, and the cyclotron period is about 7.1 milliseconds. The electrons are scattered by spatial variations in the interplanetary magnetic field. When the spatial variations are convected past a stationary spacecraft by a 500 km/sec solar wind, they are seen as temporal fluctuations at a frequency of about 3 Hz.

Dielectric surface discharges - Effects of combined low-energy and high-energy incident electrons

NASA Technical Reports Server (NTRS)

Balmain, K. G.; Hirt, W.

1983-01-01

Dielectric surface discharges affected by the addition of high energy electrons at 5 pA/sq cm to a primary 20 keV, 10 nA/sq cm electron beam with the high energy broad spectrum particles coming from the beta decay of Strontium 90 are studied. Kapton exhibits significantly increased discharge strength, increased waiting time between discharges, and a decreased number of discharges per specimen before discharge cessation. Mylar exhibits similar but less pronounced effects, while Teflon is relatively unaffected. With Kapton and Mylar, the high energy electrons act in some way to delay the instant of discharge ignition so that more charge can be accumulated and hence released during discharge. Previously announced in STAR as N82-14222

A molecularly based theory for electron transfer reorganization energy.

PubMed

Zhuang, Bilin; Wang, Zhen-Gang

2015-12-14

Using field-theoretic techniques, we develop a molecularly based dipolar self-consistent-field theory (DSCFT) for charge solvation in pure solvents under equilibrium and nonequilibrium conditions and apply it to the reorganization energy of electron transfer reactions. The DSCFT uses a set of molecular parameters, such as the solvent molecule's permanent dipole moment and polarizability, thus avoiding approximations that are inherent in treating the solvent as a linear dielectric medium. A simple, analytical expression for the free energy is obtained in terms of the equilibrium and nonequilibrium electrostatic potential profiles and electric susceptibilities, which are obtained by solving a set of self-consistent equations. With no adjustable parameters, the DSCFT predicts activation energies and reorganization energies in good agreement with previous experiments and calculations for the electron transfer between metallic ions. Because the DSCFT is able to describe the properties of the solvent in the immediate vicinity of the charges, it is unnecessary to distinguish between the inner-sphere and outer-sphere solvent molecules in the calculation of the reorganization energy as in previous work. Furthermore, examining the nonequilibrium free energy surfaces of electron transfer, we find that the nonequilibrium free energy is well approximated by a double parabola for self-exchange reactions, but the curvature of the nonequilibrium free energy surface depends on the charges of the electron-transferring species, contrary to the prediction by the linear dielectric theory.

Quantitative Simulation of QARBM Challenge Events During Radiation Belt Enhancements

NASA Astrophysics Data System (ADS)

Li, W.; Ma, Q.; Thorne, R. M.; Bortnik, J.; Chu, X.

2017-12-01

Various physical processes are known to affect energetic electron dynamics in the Earth's radiation belts, but their quantitative effects at different times and locations in space need further investigation. This presentation focuses on discussing the quantitative roles of various physical processes that affect Earth's radiation belt electron dynamics during radiation belt enhancement challenge events (storm-time vs. non-storm-time) selected by the GEM Quantitative Assessment of Radiation Belt Modeling (QARBM) focus group. We construct realistic global distributions of whistler-mode chorus waves, adopt various versions of radial diffusion models (statistical and event-specific), and use the global evolution of other potentially important plasma waves including plasmaspheric hiss, magnetosonic waves, and electromagnetic ion cyclotron waves from all available multi-satellite measurements. These state-of-the-art wave properties and distributions on a global scale are used to calculate diffusion coefficients, that are then adopted as inputs to simulate the dynamical electron evolution using a 3D diffusion simulation during the storm-time and the non-storm-time acceleration events respectively. We explore the similarities and differences in the dominant physical processes that cause radiation belt electron dynamics during the storm-time and non-storm-time acceleration events. The quantitative role of each physical process is determined by comparing against the Van Allen Probes electron observations at different energies, pitch angles, and L-MLT regions. This quantitative comparison further indicates instances when quasilinear theory is sufficient to explain the observed electron dynamics or when nonlinear interaction is required to reproduce the energetic electron evolution observed by the Van Allen Probes.

Secondary Electrons as an Energy Source for Life

NASA Astrophysics Data System (ADS)

Stelmach, Kamil B.; Neveu, Marc; Vick-Majors, Trista J.; Mickol, Rebecca L.; Chou, Luoth; Webster, Kevin D.; Tilley, Matt; Zacchei, Federica; Escudero, Cristina; Flores Martinez, Claudio L.; Labrado, Amanda; Fernández, Enrique J. G.

2018-01-01

Life on Earth is found in a wide range of environments as long as the basic requirements of a liquid solvent, a nutrient source, and free energy are met. Previous hypotheses have speculated how extraterrestrial microbial life may function, among them that particle radiation might power living cells indirectly through radiolytic products. On Earth, so-called electrophilic organisms can harness electron flow from an extracellular cathode to build biomolecules. Here, we describe two hypothetical mechanisms, termed "direct electrophy" and "indirect electrophy" or "fluorosynthesis," by which organisms could harness extracellular free electrons to synthesize organic matter, thus expanding the ensemble of potential habitats in which extraterrestrial organisms might be found in the Solar System and beyond. The first mechanism involves the direct flow of secondary electrons from particle radiation to a microbial cell to power the organism. The second involves the indirect utilization of impinging secondary electrons and a fluorescing molecule, either biotic or abiotic in origin, to drive photosynthesis. Both mechanisms involve the attenuation of an incoming particle's energy to create low-energy secondary electrons. The validity of the hypotheses is assessed through simple calculations showing the biomass density attainable from the energy supplied. Also discussed are potential survival strategies that could be used by organisms living in possible habitats with a plentiful supply of secondary electrons, such as near the surface of an icy moon. While we acknowledge that the only definitive test for the hypothesis is to collect specimens, we also describe experiments or terrestrial observations that could support or nullify the hypotheses.

Quantitative electron density characterization of soft tissue substitute plastic materials using grating-based x-ray phase-contrast imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarapata, A.; Chabior, M.; Zanette, I.

2014-10-15

Many scientific research areas rely on accurate electron density characterization of various materials. For instance in X-ray optics and radiation therapy, there is a need for a fast and reliable technique to quantitatively characterize samples for electron density. We present how a precise measurement of electron density can be performed using an X-ray phase-contrast grating interferometer in a radiographic mode of a homogenous sample in a controlled geometry. A batch of various plastic materials was characterized quantitatively and compared with calculated results. We found that the measured electron densities closely match theoretical values. The technique yields comparable results between amore » monochromatic and a polychromatic X-ray source. Measured electron densities can be further used to design dedicated X-ray phase contrast phantoms and the additional information on small angle scattering should be taken into account in order to exclude unsuitable materials.« less

Electron acceleration and kinetic energy tailoring via ultrafast terahertz fields.

PubMed

Greig, S R; Elezzabi, A Y

2014-11-17

We propose a mechanism for tuning the kinetic energy of surface plasmon generated electron pulses through control of the time delay between a pair of externally applied terahertz pulses. Varying the time delay results in translation, compression, and broadening of the kinetic energy spectrum of the generated electron pulse. We also observe that the electrons' kinetic energy dependence on the carrier envelope phase of the surface plasmon is preserved under the influence of a terahertz electric field.

Electrothermal energy conversion using electron gas volumetric change inside semiconductors

NASA Astrophysics Data System (ADS)

Yazawa, K.; Shakouri, A.

2016-07-01

We propose and analyze an electrothermal energy converter using volumetric changes in non-equilibrium electron gas inside semiconductors. The geometric concentration of electron gas under an electric field increases the effective pressure of the electrons, and then a barrier filters out cold electrons, acting like a valve. Nano- and micro-scale features enable hot electrons to arrive at the contact in a short enough time to avoid thermalization with the lattice. Key length and time scales, preliminary device geometry, and anticipated efficiency are estimated for electronic analogs of Otto and Brayton power generators and Joule-Thomson micro refrigerators on a chip. The power generators convert the energy of incident photons from the heat source to electrical current, and the refrigerator can reduce the temperature of electrons in a semiconductor device. The analytic calculations show that a large energy conversion efficiency or coefficient of performance may be possible.

Dose controlled low energy electron irradiator for biomolecular films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, S. V. K., E-mail: svkk@tifr.res.in; Tare, Satej T.; Upalekar, Yogesh V.

2016-03-15

We have developed a multi target, Low Energy Electron (LEE), precise dose controlled irradiator for biomolecular films. Up to seven samples can be irradiated one after another at any preset electron energy and dose under UHV conditions without venting the chamber. In addition, one more sample goes through all the steps except irradiation, which can be used as control for comparison with the irradiated samples. All the samples are protected against stray electron irradiation by biasing them at −20 V during the entire period, except during irradiation. Ethernet based communication electronics hardware, LEE beam control electronics and computer interface weremore » developed in house. The user Graphical User Interface to control the irradiation and dose measurement was developed using National Instruments Lab Windows CVI. The working and reliability of the dose controlled irradiator has been fully tested over the electron energy range of 0.5 to 500 eV by studying LEE induced single strand breaks to ΦX174 RF1 dsDNA.« less

Low energy electron beam processing of YBCO thin films

NASA Astrophysics Data System (ADS)

Chromik, Š.; Camerlingo, C.; Sojková, M.; Štrbík, V.; Talacko, M.; Malka, I.; Bar, I.; Bareli, G.; Jung, G.

2017-02-01

Effects of low energy 30 keV electron irradiation of superconducting YBa2Cu3O7-δ thin films have been investigated by means of transport and micro-Raman spectroscopy measurements. The critical temperature and the critical current of 200 nm thick films initially increase with increasing fluency of the electron irradiation, reach the maximum at fluency 3 - 4 × 1020 electrons/cm2, and then decrease with further fluency increase. In much thinner films (75 nm), the critical temperature increases while the critical current decreases after low energy electron irradiation with fluencies below 1020 electrons/cm2. The Raman investigations suggest that critical temperature increase in irradiated films is due to healing of broken Cusbnd O chains that results in increased carrier's concentration in superconducting CuO2 planes. Changes in the critical current are controlled by changes in the density of oxygen vacancies acting as effective pinning centers for flux vortices. The effects of low energy electron irradiation of YBCO turned out to result from a subtle balance of many processes involving oxygen removal, both by thermal activation and kick-off processes, and ordering of chains environment by incident electrons.

Target electron collision effects on energy loss straggling of protons in an electron gas at any degeneracy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barriga-Carrasco, Manuel D.

2008-03-15

The purpose of the present paper is to describe the effects of target electron collisions on proton energy loss straggling in plasmas at any degeneracy. Targets are considered fully ionized so electronic energy loss is only due to the free electrons. The analysis is focused on targets with electronic density around solid values n{sub e}{approx_equal}10{sup 23} cm{sup -3} and with temperature around T{approx_equal}10 eV; these targets are in the limit of weakly coupled electron gases. These types of plasma targets have not been studied extensively, though they are very important for inertial confinement fusion. The energy loss straggling is obtainedmore » from an exact quantum-mechanical evaluation, which takes into account the degeneracy of the target plasma, and later it is compared with common classical and degenerate approximations. Then electron collisions in the exact quantum-mechanical straggling calculation are considered. Now the energy loss straggling is enhanced for energies smaller than the energy before the maximum, then decreases around this maximum, and finally tends to the same values with respect to noncollisional calculation. Differences with the same results but not taking into account these collisions are as far as 17% in the cases analyzed. As an example, proton range distributions have been calculated to show the importance of an accurate energy straggling calculation.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roth, Friedrich; Herzig, Melanie; Knupfer, Martin

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 ofmore » 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.« less

Intrinsic Resolution of Molecular Electronic Wave Functions and Energies in Terms of Quasi-atoms and Their Interactions.

PubMed

West, Aaron C; Schmidt, Michael W; Gordon, Mark S; Ruedenberg, Klaus

2017-02-09

A general intrinsic energy resolution has been formulated for strongly correlated wave functions in the full molecular valence space and its subspaces. The information regarding the quasi-atomic organization of the molecular electronic structure is extracted from the molecular wave function without introducing any additional postulated model state wave functions. To this end, the molecular wave function is expressed in terms of quasi-atomic molecular orbitals, which maximize the overlap between subspaces of the molecular orbital space and the free-atom orbital spaces. As a result, the molecular wave function becomes the superposition of a wave function representing the juxtaposed nonbonded quasi-atoms and a wave function describing the interatomic electron migrations that create bonds through electron sharing. The juxtaposed nonbonded quasi-atoms are shown to consist of entangled quasi-atomic states from different atoms. The binding energy is resolved as a sum of contributions that are due to quasi-atom formation, quasiclassical electrostatic interactions, and interatomic interferences caused by electron sharing. The contributions are further resolved according to orbital interactions. The various transformations that generate the analysis are determined by criteria that are independent of the working orbital basis used for calculating the molecular wave function. The theoretical formulation of the resolution is quantitatively validated by an application to the C 2 molecule.

The Titan haze revisted: Magnetospheric energy sorces quantitative tholin yields

NASA Technical Reports Server (NTRS)

Thompson, W. Reid; Mcdonald, Gene D.; Sagan, Carl

1994-01-01

We present laboratory measurements of the radiation yields of complex organic solids produced from N2/CH4 gas mixtures containing 10 or 0.1% CH4. These tholins are thought to resemble organic aerosols produced in the atmospheres of Titan, Pluto, and Triton. The tholin yields are large compared to the total yield of gaseous products: nominally, 13 (C + N)/100 eV for Titan tholin and 2.1 (C + N)/100 eV for Triton tholin. High-energy magnetospheric electrons responsible for tholin production represents a class distinct from the plasma electrons considered in models of Titan's aiglow. Electrons with E greater than 20 keV provide an energy flux approximately 1 x 10(exp -2) erg/cm/sec, implying from our measured tholin yields a mass flux of 0.5 to 4.0 x 10(exp -14) g/sq cm/sec of tholin. (The corresponding thickness of the tholin sedimentary column accumulated over 4 Gyr on Titan's surface is 4 to 30 m). This figure is in agreement with required mass fluxes computed from recent radiative transfer and sedimentation models. If, however, theses results, derived from experiments at approximately 2 mb, are applied to lower pressure levels toward peak auroral electron energy deposition and scaled with pressure as the gas-phase organic yields, the derived tholin mass flux is at least an order of magnitude less. We attrribute this difference to the fact that tholin synthesis occurs well below the level of maximum electron energy depositon and to possible contributions to tholis from UV-derived C2-hydrocarbons. We conclude that Tita tholin, produced by magnetospheric electrons, is alone sufficient to supply at least a significant fraction of Titan's haze-a result consistent with the fact that the optical properties of Titan tholin, among all proposed material, are best at reproducing Titan's geometric albedo spectrum from near UV to mid-IR in light-scattering models.

Energy Harvesters for Wearable and Stretchable Electronics: From Flexibility to Stretchability.

PubMed

Wu, Hao; Huang, YongAn; Xu, Feng; Duan, Yongqing; Yin, Zhouping

2016-12-01

The rapid advancements of wearable electronics have caused a paradigm shift in consumer electronics, and the emerging development of stretchable electronics opens a new spectrum of applications for electronic systems. Playing a critical role as the power sources for independent electronic systems, energy harvesters with high flexibility or stretchability have been the focus of research efforts over the past decade. A large number of the flexible energy harvesters developed can only operate at very low strain level (≈0.1%), and their limited flexibility impedes their application in wearable or stretchable electronics. Here, the development of highly flexible and stretchable (stretchability >15% strain) energy harvesters is reviewed with emphasis on strategies of materials synthesis, device fabrication, and integration schemes for enhanced flexibility and stretchability. Due to their particular potential applications in wearable and stretchable electronics, energy-harvesting devices based on piezoelectricity, triboelectricity, thermoelectricity, and dielectric elastomers have been largely developed and the progress is summarized. The challenges and opportunities of assembly and integration of energy harvesters into stretchable systems are also discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Energy of atomic shakeoff electrons from positron decay of 37K

NASA Astrophysics Data System (ADS)

Behr, John; Fenker, Benjamin; Gorelov, Alexandre; Anholm, Melissa; Behling, Spencer; Mehlman, Michael; Melconian, Dan; Ashery, Danny; Gwinner, Gerald

2015-10-01

We have measured the low-energy atomic shakeoff electron spectrum from the β+ decay of 37K. We collect atomic electrons emitted from laser-cooled 37K using a nearly uniform electric field at low magnetic field into a position-sensitive microchannel plate. A coincidence with energetic β+s removes background. The differential position information translates to a differential electron energy spectrum. The energy spectrum from 1-100 eV is reproduced well by an analytic calculation for hydrogenic wavefunctions [Levinger PR 90 11 (1953)] using potassium quantum defects. Less than one percent of the electrons have energies higher than the 25 eV threshold for double DNA strand breaks, so relative biological effectiveness would not be altered by including these electrons. The average energy carried off by these electrons (a few eV) is smaller than expected from simple Thomas-Fermi estimates (65eV). Supported by NSERC, NRC through TRIUMF, U.S. D.O.E., State of Texas, Israel Science Foundation

The electronic states of cyclopropane studied by VUV absorption and electron energy-loss spectroscopies

NASA Astrophysics Data System (ADS)

Gingell, M.; Mason, N. J.; Walker, I. C.; Marston, G.; Zhao, H.; Siggel, M. R. F.

1999-06-01

Absolute optical (VUV) absorption cross sections for cyclopropane have been measured from 5.0 to 11.2 and 20-40 eV using synchrotron radiation. Also, electron energy-loss (EEL) spectra have been obtained using incident electrons of (a) 150 eV energy scattered through small angles (energy loss 5.0-15 eV) and (b) near-threshold energies scattered through large angles (energy loss 0-10.5 eV). Taken together these confirm that the low-lying excited electronic states of cyclopropane are of Rydberg type and, although spectral bands are diffuse, a known Rydberg series has been extended. Recent computations (Galasso V 1996 Chem. Phys. 206 289) appear to give a good account of the experimental spectrum from threshold to about 11 eV, but these must be extended if valence-excited states are to be characterized. Particular attention has been directed at the evaluation of absolute optical cross sections. These are now believed to be established over the energy ranges 5-15 and 20-40 eV. In the gap region (15-20 eV) second-order radiation may affect the optical measurements. From consideration of second-order effects, and comparison of the present studies with earlier measurements, we propose a best-estimate cross section in this energy region also.

Treatment of surfaces with low-energy electrons

NASA Astrophysics Data System (ADS)

Frank, L.; Mikmeková, E.; Lejeune, M.

2017-06-01

Electron-beam-induced deposition of various materials from suitable precursors has represented an established branch of nanotechnology for more than a decade. A specific alternative is carbon deposition on the basis of hydrocarbons as precursors that has been applied to grow various nanostructures including masks for subsequent technological steps. Our area of study was unintentional electron-beam-induced carbon deposition from spontaneously adsorbed hydrocarbon molecules. This process traditionally constitutes a challenge for scanning electron microscopy practice preventing one from performing any true surface studies outside an ultrahigh vacuum and without in-situ cleaning of samples, and also jeopardising other electron-optical devices such as electron beam lithographs. Here we show that when reducing the energy of irradiating electrons sufficiently, the e-beam-induced deposition can be converted to e-beam-induced release causing desorption of hydrocarbons and ultimate cleaning of surfaces in both an ultrahigh and a standard high vacuum. Using series of experiments with graphene samples, we demonstrate fundamental features of e-beam-induced desorption and present results of checks for possible radiation damage using Raman spectroscopy that led to optimisation of the electron energy for damage-free cleaning. The method of preventing carbon contamination described here paves the way for greatly enhanced surface sensitivity of imaging and substantially reduced demands on vacuum systems for nanotechnological applications.

A Monochromatic, Aberration-Corrected, Dual-Beam Low Energy Electron Microscope

PubMed Central

Mankos, Marian; Shadman, Khashayar

2013-01-01

The monochromatic, aberration-corrected, dual-beam low energy electron microscope (MAD-LEEM) is a novel instrument aimed at imaging of nanostructures and surfaces at sub-nanometer resolution that includes a monochromator, aberration corrector and dual beam illumination. The monochromator reduces the energy spread of the illuminating electron beam, which significantly improves spectroscopic and spatial resolution. The aberration corrector utilizes an electron mirror with negative aberrations that can be used to compensate the aberrations of the LEEM objective lens for a range of electron energies. Dual flood illumination eliminates charging generated when a conventional LEEM is used to image insulating specimens. MAD-LEEM is designed for the purpose of imaging biological and insulating specimens, which are difficult to image with conventional LEEM, Low-Voltage SEM, and TEM instruments. The MAD-LEEM instrument can also be used as a general purpose LEEM with significantly improved resolution. The low impact energy of the electrons is critical for avoiding beam damage, as high energy electrons with keV kinetic energies used in SEMs and TEMs cause irreversible change to many specimens, in particular biological materials. A potential application for MAD-LEEM is in DNA sequencing, which demands imaging techniques that enable DNA sequencing at high resolution and speed, and at low cost. The key advantages of the MAD-LEEM approach for this application are the low electron impact energies, the long read lengths, and the absence of heavy-atom DNA labeling. Image contrast simulations of the detectability of individual nucleotides in a DNA strand have been developed in order to refine the optics blur and DNA base contrast requirements for this application. PMID:23582636

A monochromatic, aberration-corrected, dual-beam low energy electron microscope.

PubMed

Mankos, Marian; Shadman, Khashayar

2013-07-01

The monochromatic, aberration-corrected, dual-beam low energy electron microscope (MAD-LEEM) is a novel instrument aimed at imaging of nanostructures and surfaces at sub-nanometer resolution that includes a monochromator, aberration corrector and dual beam illumination. The monochromator reduces the energy spread of the illuminating electron beam, which significantly improves spectroscopic and spatial resolution. The aberration corrector utilizes an electron mirror with negative aberrations that can be used to compensate the aberrations of the LEEM objective lens for a range of electron energies. Dual flood illumination eliminates charging generated when a conventional LEEM is used to image insulating specimens. MAD-LEEM is designed for the purpose of imaging biological and insulating specimens, which are difficult to image with conventional LEEM, Low-Voltage SEM, and TEM instruments. The MAD-LEEM instrument can also be used as a general purpose LEEM with significantly improved resolution. The low impact energy of the electrons is critical for avoiding beam damage, as high energy electrons with keV kinetic energies used in SEMs and TEMs cause irreversible change to many specimens, in particular biological materials. A potential application for MAD-LEEM is in DNA sequencing, which demands imaging techniques that enable DNA sequencing at high resolution and speed, and at low cost. The key advantages of the MAD-LEEM approach for this application are the low electron impact energies, the long read lengths, and the absence of heavy-atom DNA labeling. Image contrast simulations of the detectability of individual nucleotides in a DNA strand have been developed in order to refine the optics blur and DNA base contrast requirements for this application. Copyright © 2013 Elsevier B.V. All rights reserved.

Low-energy plasma focus device as an electron beam source.

PubMed

Khan, Muhammad Zubair; Ling, Yap Seong; Yaqoob, Ibrar; Kumar, Nitturi Naresh; Kuang, Lim Lian; San, Wong Chiow

2014-01-01

A low-energy plasma focus device was used as an electron beam source. A technique was developed to simultaneously measure the electron beam intensity and energy. The system was operated in Argon filling at an optimum pressure of 1.7 mbar. A Faraday cup was used together with an array of filtered PIN diodes. The beam-target X-rays were registered through X-ray spectrometry. Copper and lead line radiations were registered upon usage as targets. The maximum electron beam charge and density were estimated to be 0.31 μC and 13.5 × 10(16)/m(3), respectively. The average energy of the electron beam was 500 keV. The high flux of the electron beam can be potentially applicable in material sciences.

Experimental insights on the electron transfer and energy transfer processes between Ce{sup 3+}-Yb{sup 3+} and Ce{sup 3+}-Tb{sup 3+} in borate glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sontakke, Atul D., E-mail: sontakke.atul.55a@st.kyoto-u.ac.jp; Katayama, Yumiko; Tanabe, Setsuhisa

2015-03-30

A facile method to describe the electron transfer and energy transfer processes among lanthanide ions is presented based on the temperature dependent donor luminescence decay kinetics. The electron transfer process in Ce{sup 3+}-Yb{sup 3+} exhibits a steady rise with temperature, whereas the Ce{sup 3+}-Tb{sup 3+} energy transfer remains nearly unaffected. This feature has been investigated using the rate equation modeling and a methodology for the quantitative estimation of interaction parameters is presented. Moreover, the overall consequences of electron transfer and energy transfer process on donor-acceptor luminescence behavior, quantum efficiency, and donor luminescence decay kinetics are discussed in borate glass host.more » The results in this study propose a straight forward approach to distinguish the electron transfer and energy transfer processes between lanthanide ions in dielectric hosts, which is highly advantageous in view of the recent developments on lanthanide doped materials for spectral conversion, persistent luminescence, and related applications.« less

Decomposition reaction of the veterinary antibiotic ciprofloxacin using electron ionizing energy.

PubMed

Cho, Jae Young; Chung, Byung Yeoup; Lee, Kyeong-Bo; Lee, Geon-Hwi; Hwang, Seon Ah

2014-12-01

The application of electron ionizing energy for degrading veterinary antibiotic ciprofloxacin (CFX) in aqueous solution was elucidated. The degradation efficiency of CFX after irradiation with electron ionizing energy was 38% at 1 kGy, 80% at 5kGy, and 97% at 10 kGy. Total organic carbon of CFX in aqueous solution after irradiation with electron ionizing energy decreased 2% at 1 kGy, 18% at 5 kGy, and 53% at 10 kGy. The CFX degradation products after irradiation with electron ionizing energy were CFX1 ([M+H] m/z 330), CFX2 ([M+H] m/z 314), and CFX3 ([M+H] m/z 263). CFX1 had an F atom substituted with OH and CFX2 was expected to originate from CFX via loss of F or H2O. CFX3 was expected to originate from CFX via loss of the piperazynilic ring. Among the several radicals, hydrate electron (eaq(-)) is expected to play an important role in degradation of veterinary antibiotic during irradiation with electron ionizing energy. The toxicity of the degraded products formed during irradiation with electron ionizing energy was evaluated using microbes such as Escherichia coli, Pseudomonas putida, and Bacillus subtilis, and the results revealed that the toxicity decreased with irradiation. These results demonstrate that irradiation technology using electron ionizing energy is an effective was to remove veterinary antibiotics from an aquatic ecosystem. Copyright © 2014 Elsevier Ltd. All rights reserved.

Why do Electrons with "Anomalous Energies" appear in High-Pressure Gas Discharges?

NASA Astrophysics Data System (ADS)

Kozyrev, Andrey; Kozhevnikov, Vasily; Semeniuk, Natalia

2018-01-01

Experimental studies connected with runaway electron beams generation convincingly shows the existence of electrons with energies above the maximum voltage applied to the discharge gap. Such electrons are also known as electrons with "anomalous energies". We explain the presence of runaway electrons having so-called "anomalous energies" according to physical kinetics principles, namely, we describe the total ensemble of electrons with the distribution function. Its evolution obeys Boltzmann kinetic equation. The dynamics of self-consistent electromagnetic field is taken into the account by adding complete Maxwell's equation set to the resulting system of equations. The electrodynamic mechanism of the interaction of electrons with a travelling-wave electric field is analyzed in details. It is responsible for the appearance of electrons with high energies in real discharges.

Free electron lasers for transmission of energy in space

NASA Technical Reports Server (NTRS)

Segall, S. B.; Hiddleston, H. R.; Catella, G. C.

1981-01-01

A one-dimensional resonant-particle model of a free electron laser (FEL) is used to calculate laser gain and conversion efficiency of electron energy to photon energy. The optical beam profile for a resonant optical cavity is included in the model as an axial variation of laser intensity. The electron beam profile is matched to the optical beam profile and modeled as an axial variation of current density. Effective energy spread due to beam emittance is included. Accelerators appropriate for a space-based FEL oscillator are reviewed. Constraints on the concentric optical resonator and on systems required for space operation are described. An example is given of a space-based FEL that would produce 1.7 MW of average output power at 0.5 micrometer wavelength with over 50% conversion efficiency of electrical energy to laser energy. It would utilize a 10 m-long amplifier centered in a 200 m-long optical cavity. A 3-amp, 65 meV electrostatic accelerator would provide the electron beam and recover the beam after it passes through the amplifier. Three to five shuttle flights would be needed to place the laser in orbit.

Energy of auroral electrons and Z mode generation

NASA Technical Reports Server (NTRS)

Krauss-Varban, D.; Wong, H. K.

1990-01-01

The present consideration of Z-mode radiation generation, in light of observational results indicating that the O mode and second-harmonic X-mode emissions can prevail over the X-mode fundamental radiation when suprathermal electron energy is low, gives attention to whether the thermal effect on the Z-mode dispersion can be equally important, and whether the Z-mode can compete for the available free-energy source. It is found that, under suitable circumstances, the growth rate of the Z-mode can be substantial even for low suprathermal auroral electron energies. Growth is generally maximized for propagation perpendicular to the magnetic field.

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.

Permanent-magnet energy spectrometer for electron beams from radiotherapy accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

McLaughlin, David J.; Shikhaliev, Polad M.; Matthews, Kenneth L.

2015-09-15

Purpose: The purpose of this work was to adapt a lightweight, permanent magnet electron energy spectrometer for the measurement of energy spectra of therapeutic electron beams. Methods: An irradiation geometry and measurement technique were developed for an approximately 0.54-T, permanent dipole magnet spectrometer to produce suitable latent images on computed radiography (CR) phosphor strips. Dual-pinhole electron collimators created a 0.318-cm diameter, approximately parallel beam incident on the spectrometer and an appropriate dose rate at the image plane (CR strip location). X-ray background in the latent image, reduced by a 7.62-cm thick lead block between the pinhole collimators, was removed usingmore » a fitting technique. Theoretical energy-dependent detector response functions (DRFs) were used in an iterative technique to transform CR strip net mean dose profiles into energy spectra on central axis at the entrance to the spectrometer. These spectra were transformed to spectra at 95-cm source to collimator distance (SCD) by correcting for the energy dependence of electron scatter. The spectrometer was calibrated by comparing peak mean positions in the net mean dose profiles, initially to peak mean energies determined from the practical range of central-axis percent depth-dose (%DD) curves, and then to peak mean energies that accounted for how the collimation modified the energy spectra (recalibration). The utility of the spectrometer was demonstrated by measuring the energy spectra for the seven electron beams (7–20 MeV) of an Elekta Infinity radiotherapy accelerator. Results: Plots of DRF illustrated their dependence on energy and position in the imaging plane. Approximately 15 iterations solved for the energy spectra at the spectrometer entrance from the measured net mean dose profiles. Transforming those spectra into ones at 95-cm SCD increased the low energy tail of the spectra, while correspondingly decreasing the peaks and shifting them to

Permanent-magnet energy spectrometer for electron beams from radiotherapy accelerators.

PubMed

McLaughlin, David J; Hogstrom, Kenneth R; Carver, Robert L; Gibbons, John P; Shikhaliev, Polad M; Matthews, Kenneth L; Clarke, Taylor; Henderson, Alexander; Liang, Edison P

2015-09-01

The purpose of this work was to adapt a lightweight, permanent magnet electron energy spectrometer for the measurement of energy spectra of therapeutic electron beams. An irradiation geometry and measurement technique were developed for an approximately 0.54-T, permanent dipole magnet spectrometer to produce suitable latent images on computed radiography (CR) phosphor strips. Dual-pinhole electron collimators created a 0.318-cm diameter, approximately parallel beam incident on the spectrometer and an appropriate dose rate at the image plane (CR strip location). X-ray background in the latent image, reduced by a 7.62-cm thick lead block between the pinhole collimators, was removed using a fitting technique. Theoretical energy-dependent detector response functions (DRFs) were used in an iterative technique to transform CR strip net mean dose profiles into energy spectra on central axis at the entrance to the spectrometer. These spectra were transformed to spectra at 95-cm source to collimator distance (SCD) by correcting for the energy dependence of electron scatter. The spectrometer was calibrated by comparing peak mean positions in the net mean dose profiles, initially to peak mean energies determined from the practical range of central-axis percent depth-dose (%DD) curves, and then to peak mean energies that accounted for how the collimation modified the energy spectra (recalibration). The utility of the spectrometer was demonstrated by measuring the energy spectra for the seven electron beams (7-20 MeV) of an Elekta Infinity radiotherapy accelerator. Plots of DRF illustrated their dependence on energy and position in the imaging plane. Approximately 15 iterations solved for the energy spectra at the spectrometer entrance from the measured net mean dose profiles. Transforming those spectra into ones at 95-cm SCD increased the low energy tail of the spectra, while correspondingly decreasing the peaks and shifting them to slightly lower energies. Energy calibration

Frequency chirping for resonance-enhanced electron energy during laser acceleration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, D.N.; Suk, H.

2006-04-15

The model given by Singh-Tripathi [Phys. Plasmas 11, 743 (2004)] for laser electron acceleration in a magnetic wiggler is revisited by including the effect of laser frequency chirping. Laser frequency chirp helps to maintain the resonance condition longer, which increases the electron energy gain. A significant enhancement in electron energy gain during laser acceleration is observed.

Probing the effect of electron channelling on atomic resolution energy dispersive X-ray quantification.

PubMed

MacArthur, Katherine E; Brown, Hamish G; Findlay, Scott D; Allen, Leslie J

2017-11-01

Advances in microscope stability, aberration correction and detector design now make it readily possible to achieve atomic resolution energy dispersive X-ray mapping for dose resilient samples. These maps show impressive atomic-scale qualitative detail as to where the elements reside within a given sample. Unfortunately, while electron channelling is exploited to provide atomic resolution data, this very process makes the images rather more complex to interpret quantitatively than if no electron channelling occurred. Here we propose small sample tilt as a means for suppressing channelling and improving quantification of composition, whilst maintaining atomic-scale resolution. Only by knowing composition and thickness of the sample is it possible to determine the atomic configuration within each column. The effects of neighbouring atomic columns with differing composition and of residual channelling on our ability to extract exact column-by-column composition are also discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

Cubic Calorimeter for High-Energy Electrons in Ultra-Long Ballooning

NASA Technical Reports Server (NTRS)

Moiseev, Alexander A.; Mitchell, John W.; Ormes, Jonathan F.; Streitmatter, Robert E.

2003-01-01

The concept and optimization study of a balloon-borne instrument to study high-energy (from 100 GeV to 5 TeV) cosmic ray electrons will be presented. This energy range of electrons is very interesting for the study of cosmic ray propagation and the search for the nearby sources of high-energy electrons. The instrument is based on a cubic design that allows the detection from all sides. Proton rejection is provided by stringent track analysis, which allows defining when an electron shower is exhausted while the hadron shower continues development. The collecting power of a nominal balloon-borne instrument using this concept will be over 2 square meters sr. This will provide approximately 3,000 electron events above 500 GeV for 3-month long ULDB flight. This instrument will also be capable of detecting sharp features in the high energy gamma-ray spectrum such as gamma-ray lines originating from the dark matter annihilation.

Parallel electron force balance and the L-H transition

DOE PAGES

Stoltzfus-Dueck, T.

2016-05-23

In one popular paradigm for the L-H transition, energy transfer to the mean flows directly depletes turbulence fluctuation energy, resulting in suppression of the turbulence and a corresponding transport bifurcation. To quantitatively evaluate this mechanism, one must remember that electron parallel force balance couples nonzonal velocity fluctuations with electron pressure fluctuations on rapid timescales, comparable with the electron transit time. For this reason, energy in the nonzonal velocity stays in a fairly fixed ratio to the free energy in electron density fluctuations, at least for frequency scales much slower than electron transit. Furthermore, in order for direct depletion of themore » energy in turbulent fluctuations to cause the L-H transition, energy transfer via Reynolds stress must therefore drain enough energy to significantly reduce the sum of the free energy in nonzonal velocities and electron pressure fluctuations. At low k⊥, the electron thermal free energy is much larger than the energy in nonzonal velocities, posing a stark challenge for this model of the L-H transition.« less

Electrothermal energy conversion using electron gas volumetric change inside semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yazawa, K.; Shakouri, A.

2016-07-25

We propose and analyze an electrothermal energy converter using volumetric changes in non-equilibrium electron gas inside semiconductors. The geometric concentration of electron gas under an electric field increases the effective pressure of the electrons, and then a barrier filters out cold electrons, acting like a valve. Nano- and micro-scale features enable hot electrons to arrive at the contact in a short enough time to avoid thermalization with the lattice. Key length and time scales, preliminary device geometry, and anticipated efficiency are estimated for electronic analogs of Otto and Brayton power generators and Joule-Thomson micro refrigerators on a chip. The powermore » generators convert the energy of incident photons from the heat source to electrical current, and the refrigerator can reduce the temperature of electrons in a semiconductor device. The analytic calculations show that a large energy conversion efficiency or coefficient of performance may be possible.« less

Deceleration processes of secondary electrons produced by a high-energy Auger electron in a biological context.

PubMed

Kai, Takeshi; Yokoya, Akinari; Ukai, Masatoshi; Fujii, Kentaro; Watanabe, Ritsuko

2016-11-01

To simulate the deceleration processes of secondary electrons produced by a high-energy Auger electron in water, and particularly to focus on the spatial and temporal distributions of the secondary electron and the collision events (e.g. ionization, electronic excitation, and dissociative electron attachment) that are involved in the multiplication of lesions at sites of DNA damage. We developed a dynamic Monte Carlo code that considers the Coulombic force between an ejected electron and its parent cation produced by the Auger electron in water. Thus our code can simulate some return electrons to the parent cations. Using the code, we calculated to within the order of femtoseconds the temporal evolution of collision events, the mean energy, and the mean traveling distance (including its spatial probability distribution) of the electron at an ejected energy of 20 eV. Some of the decelerating electrons in water in the Coulombic field were attracted to the ionized atoms (cations) by the Coulombic force within hundreds of femtoseconds, although the force did not significantly enhance the number of ionization, electronic excitation, and dissociative electron attachment collision events leading to water radiolysis. The secondary electrons are decelerated in water by the Coulombic force and recombined to the ionized atoms (cations). Furthermore, the some return electrons might be prehydrated in water layer near the parent cation in DNA if the electrons might be emitted from the DNA. The prehydrated electron originated from the return electron might play a significant role in inducing DNA damage.

Energy-resolved coherent diffraction from laser-driven electronic motion in atoms

NASA Astrophysics Data System (ADS)

Shao, Hua-Chieh; Starace, Anthony F.

2017-10-01

We investigate theoretically the use of energy-resolved ultrafast electron diffraction to image laser-driven electronic motion in atoms. A chirped laser pulse is used to transfer the valence electron of the lithium atom from the ground state to the first excited state. During this process, the electronic motion is imaged by 100-fs and 1-fs electron pulses in energy-resolved diffraction measurements. Simulations show that the angle-resolved spectra reveal the time evolution of the energy content and symmetry of the electronic state. The time-dependent diffraction patterns are further interpreted in terms of the momentum transfer. For the case of incident 1-fs electron pulses, the rapid 2 s -2 p quantum beat motion of the target electron is imaged as a time-dependent asymmetric oscillation of the diffraction pattern.

Electron transport in furfural: dependence of the electron ranges on the cross sections and the energy loss distribution functions

NASA Astrophysics Data System (ADS)

Ellis-Gibbings, L.; Krupa, K.; Colmenares, R.; Blanco, F.; Muńoz, A.; Mendes, M.; Ferreira da Silva, F.; Limá Vieira, P.; Jones, D. B.; Brunger, M. J.; García, G.

2016-09-01

Recent theoretical and experimental studies have provided a complete set of differential and integral electron scattering cross section data from furfural over a broad energy range. The energy loss distribution functions have been determined in this study by averaging electron energy loss spectra for different incident energies and scattering angles. All these data have been used as input parameters for an event by event Monte Carlo simulation procedure to obtain the electron energy deposition patterns and electron ranges in liquid furfural. The dependence of these results on the input cross sections is then analysed to determine the uncertainty of the simulated values.

Applications in Energy, Optics and Electronics.

ERIC Educational Resources Information Center

Rosenberg, Robert; And Others

1980-01-01

Discusses the applications of thin films in energy, optics and electronics. The use of thin-film technologies for heat mirrors, anti-reflection coatings, interference filters, solar cells, and metal contacts is included. (HM)

High Energy Electron Detectors on Sphinx

NASA Astrophysics Data System (ADS)

Thompson, J. R.; Porte, A.; Zucchini, F.; Calamy, H.; Auriel, G.; Coleman, P. L.; Bayol, F.; Lalle, B.; Krishnan, M.; Wilson, K.

2008-11-01

Z-pinch plasma radiation sources are used to dose test objects with K-shell (˜1-4keV) x-rays. The implosion physics can produce high energy electrons (> 50keV), which could distort interpretation of the soft x-ray effects. We describe the design and implementation of a diagnostic suite to characterize the electron environment of Al wire and Ar gas puff z-pinches on Sphinx. The design used ITS calculations to model detector response to both soft x-rays and electrons and help set upper bounds to the spurious electron flux. Strategies to discriminate between the known soft x-ray emission and the suspected electron flux will be discussed. H.Calamy et al, ``Use of microsecond current prepulse for dramatic improvements of wire array Z-pinch implosion,'' Phys Plasmas 15, 012701 (2008) J.A.Halbleib et al, ``ITS: the integrated TIGER series of electron/photon transport codes-Version 3.0,'' IEEE Trans on Nuclear Sci, 39, 1025 (1992)

Kinetic energy of shakeoff atomic electrons from 37K β+ decay

NASA Astrophysics Data System (ADS)

Behr, J. A.; Gorelov, A.; Farfan, C.; Smale, S.; Olchanski, K.; Kurchananov, L.; Anholm, M.; Behling, R. S.; Fenker, B.; Shidling, P. D.; Mehlman, M.; Melconian, D.; Ashery, D.; Gwinner, G.; Trinat Collaboration

2013-10-01

We have measured the kinetic energies from 0 to 30 eV of atomic shakeoff electrons from the β+ decay of 37K. Despite much experimental and theoretical work on the distribution of final ion charge states, shakeoff electrons from β- decay have only been measured with energies above 150 eV [Mitrokhovich, Nucl. Phys. Atom. Energy, 11, 125 (2010)]. We use our magneto-optical trap's time-varying magnetic quadrupole field combined with a uniform electric field as a spectrometer. Our result has more 15 eV electrons than a model using the sudden approximation and hydrogenic wavefunctions [Levinger, Phys. Rev. 90, 11 (1958)]. The total energy carried away by electrons is, as expected, a negligible correction to superallowed Ft values. Understanding the energy of these low-energy electrons is important for their use in precision β decay to select events coming from trapped atoms and start time-of-flight for the recoil ions. Our results could provide a benchmark for shakeoff electron calculations used for biological radiation damage [Lee, Comp. Math. Meth in Medicine doi:10.1155/2012/651475]. Support: NSERC, NRC through TRIUMF, DOE ER41747 ER40773, State of Texas, Israel Science Foundation.

Imaging of nonlocal hot-electron energy dissipation via shot noise.

PubMed

Weng, Qianchun; Komiyama, Susumu; Yang, Le; An, Zhenghua; Chen, Pingping; Biehs, Svend-Age; Kajihara, Yusuke; Lu, Wei

2018-05-18

In modern microelectronic devices, hot electrons accelerate, scatter, and dissipate energy in nanoscale dimensions. Despite recent progress in nanothermometry, direct real-space mapping of hot-electron energy dissipation is challenging because existing techniques are restricted to probing the lattice rather than the electrons. We realize electronic nanothermometry by measuring local current fluctuations, or shot noise, associated with ultrafast hot-electron kinetic processes (~21 terahertz). Exploiting a scanning and contact-free tungsten tip as a local noise probe, we directly visualize hot-electron distributions before their thermal equilibration with the host gallium arsenide/aluminium gallium arsenide crystal lattice. With nanoconstriction devices, we reveal unexpected nonlocal energy dissipation at room temperature, which is reminiscent of ballistic transport of low-temperature quantum conductors. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Low-Energy Plasma Focus Device as an Electron Beam Source

PubMed Central

Seong Ling, Yap; Naresh Kumar, Nitturi; Lian Kuang, Lim; Chiow San, Wong

2014-01-01

A low-energy plasma focus device was used as an electron beam source. A technique was developed to simultaneously measure the electron beam intensity and energy. The system was operated in Argon filling at an optimum pressure of 1.7 mbar. A Faraday cup was used together with an array of filtered PIN diodes. The beam-target X-rays were registered through X-ray spectrometry. Copper and lead line radiations were registered upon usage as targets. The maximum electron beam charge and density were estimated to be 0.31 μC and 13.5 × 1016/m3, respectively. The average energy of the electron beam was 500 keV. The high flux of the electron beam can be potentially applicable in material sciences. PMID:25544952

Core level electron energy-loss spectra of minerals: pre-edge fine structures at the oxygen K-edge . Comment on ``Water in minerals detectable by electron energy-loss spectroscopy EELS'' by R. Wirth, Phys Chem Minerals (1997) 24:561-568

NASA Astrophysics Data System (ADS)

van Aken, P. A.; Liebscher, B.; Styrsa, V. J.

In a recent paper entitled ``Water in minerals detectable by electron energy-loss spectroscopy EELS'' by R. Wirth, it has been claimed that OH-- and H2O-bearing minerals exhibit a characteristic peak in the ELNES spectra at about 528 eV prior to the onset of the O K-edge at 532 eV, which could be used for (semi-)quantitative determination of water- or OH-contents on a nanometer scale. It is shown here by parallel electron energy-loss spectroscopy (PEELS) recorded in a transmission electron microscope (TEM) that O K-pre-edge peaks with very high intensities may also exist in water-free compounds and minerals, in particular when they contain transition metals. These spectral features arise from covalent mixing of the metal and oxygen states, which introduces oxygen p character in unoccupied states of mainly metal character. The point is illustrated by the comparison of hematite (α-Fe2O3) and lepidocrocite (γ-FeOOH) O K-edge PEELS spectra which exhibit similar intensities of the pre-edge peak, despite of their grossly different OH- contents. As a consequence, the general validity of the method proposed by Wirth is questioned.

Simulation of electron transport during electron-beam-induced deposition of nanostructures

PubMed Central

Jeschke, Harald O; Valentí, Roser

2013-01-01

Summary We present a numerical investigation of energy and charge distributions during electron-beam-induced growth of tungsten nanostructures on SiO2 substrates by using a Monte Carlo simulation of the electron transport. This study gives a quantitative insight into the deposition of energy and charge in the substrate and in the already existing metallic nanostructures in the presence of the electron beam. We analyze electron trajectories, inelastic mean free paths, and the distribution of backscattered electrons in different compositions and at different depths of the deposit. We find that, while in the early stages of the nanostructure growth a significant fraction of electron trajectories still interacts with the substrate, when the nanostructure becomes thicker the transport takes place almost exclusively in the nanostructure. In particular, a larger deposit density leads to enhanced electron backscattering. This work shows how mesoscopic radiation-transport techniques can contribute to a model that addresses the multi-scale nature of the electron-beam-induced deposition (EBID) process. Furthermore, similar simulations can help to understand the role that is played by backscattered electrons and emitted secondary electrons in the change of structural properties of nanostructured materials during post-growth electron-beam treatments. PMID:24367747

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.

Electron-Beam Diagnostic Methods for Hypersonic Flow Diagnostics

NASA Technical Reports Server (NTRS)

1994-01-01

The purpose of this work was the evaluation of the use of electron-bean fluorescence for flow measurements during hypersonic flight. Both analytical and numerical models were developed in this investigation to evaluate quantitatively flow field imaging concepts based upon the electron beam fluorescence technique for use in flight research and wind tunnel applications. Specific models were developed for: (1) fluorescence excitation/emission for nitrogen, (2) rotational fluorescence spectrum for nitrogen, (3) single and multiple scattering of electrons in a variable density medium, (4) spatial and spectral distribution of fluorescence, (5) measurement of rotational temperature and density, (6) optical filter design for fluorescence imaging, and (7) temperature accuracy and signal acquisition time requirements. Application of these models to a typical hypersonic wind tunnel flow is presented. In particular, the capability of simulating the fluorescence resulting from electron impact ionization in a variable density nitrogen or air flow provides the capability to evaluate the design of imaging instruments for flow field mapping. The result of this analysis is a recommendation that quantitative measurements of hypersonic flow fields using electron-bean fluorescence is a tractable method with electron beam energies of 100 keV. With lower electron energies, electron scattering increases with significant beam divergence which makes quantitative imaging difficult. The potential application of the analytical and numerical models developed in this work is in the design of a flow field imaging instrument for use in hypersonic wind tunnels or onboard a flight research vehicle.

A Quantitative Exploration of the Relationship between Patient Health and Electronic Personal Health Records

ERIC Educational Resources Information Center

Hines, Denise Williams

2009-01-01

The use of electronic personal health records is becoming increasingly more popular as healthcare providers, healthcare and government leaders, and patients are seeking ways to improve healthcare quality and to decrease costs (Abrahamsen, 2007). This quantitative, descriptive correlational study examined the relationship between the degree of…

Inter-satellite calibration of FengYun 3 medium energy electron fluxes with POES electron measurements

NASA Astrophysics Data System (ADS)

Zhang, Yang; Ni, Binbin; Xiang, Zheng; Zhang, Xianguo; Zhang, Xiaoxin; Gu, Xudong; Fu, Song; Cao, Xing; Zou, Zhengyang

2018-05-01

We perform an L-shell dependent inter-satellite calibration of FengYun 3 medium energy electron measurements with POES measurements based on rough orbital conjunctions within 5 min × 0.1 L × 0.5 MLT. By comparing electron flux data between the U.S. Polar Orbiting Environmental Satellites (POES) and Chinese sun-synchronous satellites including FY-3B and FY-3C for a whole year of 2014, we attempt to remove less reliable data and evaluate systematic uncertainties associated with the FY-3B and FY-3C datasets, expecting to quantify the inter-satellite calibration factors for the 150-350 keV energy channel at L = 2-7. Compared to the POES data, the FY-3B and FY-3C data generally exhibit a similar trend of electron flux variations but more or less underestimate them within a factor of 5 for the medium electron energy 150-350 keV channel. Good consistency in the flux conjunctions after the inter-calibration procedures gives us certain confidence to generalize our method to calibrate electron flux measurements from various satellite instruments.

Quantitation of absorbed or deposited materials on a substrate that measures energy deposition

DOEpatents

Grant, Patrick G.; Bakajin, Olgica; Vogel, John S.; Bench, Graham

2005-01-18

This invention provides a system and method for measuring an energy differential that correlates to quantitative measurement of an amount mass of an applied localized material. Such a system and method remains compatible with other methods of analysis, such as, for example, quantitating the elemental or isotopic content, identifying the material, or using the material in biochemical analysis.

Electronic structures of elements according to ionization energies.

PubMed

Zadeh, Dariush H

2017-11-28

The electronic structures of elements in the periodic table were analyzed using available experimental ionization energies. Two new parameters were defined to carry out the study. The first parameter-apparent nuclear charge (ANC)-quantified the overall charge of the nucleus and inner electrons observed by an outer electron during the ionization process. This parameter was utilized to define a second parameter, which presented the shielding ability of an electron against the nuclear charge. This second parameter-electron shielding effect (ESE)-provided an insight into the electronic structure of atoms. This article avoids any sort of approximation, interpolation or extrapolation. First experimental ionization energies were used to obtain the two aforementioned parameters. The second parameter (ESE) was then graphed against the electron number of each element, and was used to read the corresponding electronic structure. The ESE showed spikes/peaks at the end of each electronic shell, providing insight into when an electronic shell closes and a new one starts. The electronic structures of elements in the periodic table were mapped using this methodology. These graphs did not show complete agreement with the previously known "Aufbau" filling rule. A new filling rule was suggested based on the present observations. Finally, a new way to organize elements in the periodic table is suggested. Two earlier topics of effective nuclear charge, and shielding factor were also briefly discussed and compared numerically to demonstrate the capability of the new approach.

End-boundary sheath potential, electron and ion energy distribution in the low-pressure non-ambipolar electron plasma

NASA Astrophysics Data System (ADS)

Chen, Lee; Chen, Zhiying; Funk, Merritt

2013-12-01

The end-boundary floating-surface sheath potential, electron and ion energy distribution functions (EEDf, IEDf) in the low-pressure non-ambipolar electron plasma (NEP) are investigated. The NEP is heated by an electron beam extracted from an inductively coupled electron-source plasma (ICP) through a dielectric injector by an accelerator located inside the NEP. This plasma's EEDf has a Maxwellian bulk followed by a broad energy continuum connecting to the most energetic group with energies around the beam energy. The NEP pressure is 1-3 mTorr of N2 and the ICP pressure is 5-15 mTorr of Ar. The accelerator is biased positively from 80 to 600 V and the ICP power range is 200-300 W. The NEP EEDf and IEDf are determined using a retarding field energy analyser. The EEDf and IEDf are measured at various NEP pressures, ICP pressures and powers as a function of accelerator voltage. The accelerator current and sheath potential are also measured. The IEDf reveals mono-energetic ions with adjustable energy and it is proportionally controlled by the sheath potential. The NEP end-boundary floating surface is bombarded by a mono-energetic, space-charge-neutral plasma beam. When the injected energetic electron beam is adequately damped by the NEP, the sheath potential is linearly controlled at almost a 1 : 1 ratio by the accelerator voltage. If the NEP parameters cannot damp the electron beam sufficiently, leaving an excess amount of electron-beam power deposited on the floating surface, the sheath potential will collapse and become unresponsive to the accelerator voltage.

Sustainably powering wearable electronics solely by biomechanical energy

PubMed Central

Wang, Jie; Li, Shengming; Yi, Fang; Zi, Yunlong; Lin, Jun; Wang, Xiaofeng; Xu, Youlong; Wang, Zhong Lin

2016-01-01

Harvesting biomechanical energy is an important route for providing electricity to sustainably drive wearable electronics, which currently still use batteries and therefore need to be charged or replaced/disposed frequently. Here we report an approach that can continuously power wearable electronics only by human motion, realized through a triboelectric nanogenerator (TENG) with optimized materials and structural design. Fabricated by elastomeric materials and a helix inner electrode sticking on a tube with the dielectric layer and outer electrode, the TENG has desirable features including flexibility, stretchability, isotropy, weavability, water-resistance and a high surface charge density of 250 μC m−2. With only the energy extracted from walking or jogging by the TENG that is built in outsoles, wearable electronics such as an electronic watch and fitness tracker can be immediately and continuously powered. PMID:27677971

Low-energy particle experiments-electron analyzer (LEPe) onboard the Arase spacecraft

NASA Astrophysics Data System (ADS)

Kazama, Yoichi; Wang, Bo-Jhou; Wang, Shiang-Yu; Ho, Paul T. P.; Tam, Sunny W. Y.; Chang, Tzu-Fang; Chiang, Chih-Yu; Asamura, Kazushi

2017-12-01

In this report, we describe the low-energy electron instrument LEPe (low-energy particle experiments-electron analyzer) onboard the Arase (ERG) spacecraft. The instrument measures a three-dimensional distribution function of electrons with energies of ˜ 19 eV-19 keV. Electrons in this energy range dominate in the inner magnetosphere, and measurement of such electrons is important in terms of understanding the magnetospheric dynamics and wave-particle interaction. The instrument employs a toroidal tophat electrostatic energy analyzer with a passive 6-mm aluminum shield. To minimize background radiation effects, the analyzer has a background channel, which monitors counts produced by background radiation. Background counts are then subtracted from measured counts. Electronic components are radiation tolerant, and 5-mm-thick shielding of the electronics housing ensures that the total dose is less than 100 kRad for the one-year nominal mission lifetime. The first in-space measurement test was done on February 12, 2017, showing that the instrument functions well. On February 27, the first all-instrument run test was done, and the LEPe instrument measured an energy dispersion event probably related to a substorm injection occurring immediately before the instrument turn-on. These initial results indicate that the instrument works fine in space, and the measurement performance is good for science purposes.[Figure not available: see fulltext.

Quantitative analysis of weak interactions by Lattice energy calculation, Hirshfeld surface and DFT studies of sulfamonomethoxine

NASA Astrophysics Data System (ADS)

Patel, Kinjal D.; Patel, Urmila H.

2017-01-01

Sulfamonomethoxine, 4-Amino-N-(6-methoxy-4-pyrimidinyl) benzenesulfonamide (C11H12N4O3S), is investigated by single crystal X-ray diffraction technique. Pair of N-H⋯N and C-H⋯O intermolecular interactions along with π···π interaction are responsible for the stability of the molecular packing of the structure. In order to understand the nature of the interactions and their quantitative contributions towards the crystal packing, the 3D Hirshfeld surface and 2D fingerprint plot analysis are carried out. PIXEL calculations are performed to determine the lattice energies correspond to intermolecular interactions in the crystal structure. Ab initio quantum chemical calculations of sulfamonomethoxine (SMM) have been performed by B3LYP method, using 6-31G** basis set with the help of Schrodinger software. The computed geometrical parameters are in good agreement with the experimental data. The Mulliken charge distribution, calculated using B3LYP method to confirm the presence of electron acceptor and electron donor atoms, responsible for intermolecular hydrogen bond interactions hence the molecular stability.

Electronic Devices and Systems. Energy Technology Series.

ERIC Educational Resources Information Center

Technical Education Research Centre-Southwest, Waco, TX.

This course in electronic devices and systems is one of 16 courses in the Energy Technology Series developed for an Energy Conservation-and-Use Technology curriculum. Intended for use in two-year postsecondary technical institutions to prepare technicians for employment, the courses are also useful in industry for updating employees in…

Recent advances in electronic structure theory and their influence on the accuracy of ab initio potential energy surfaces

NASA Technical Reports Server (NTRS)

Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Taylor, Peter R.

1989-01-01

Recent advances in electronic structure theory and the availability of high speed vector processors have substantially increased the accuracy of ab initio potential energy surfaces. The recently developed atomic natural orbital approach for basis set contraction has reduced both the basis set incompleteness and superposition errors in molecular calculations. Furthermore, full CI calculations can often be used to calibrate a CASSCF/MRCI approach that quantitatively accounts for the valence correlation energy. These computational advances also provide a vehicle for systematically improving the calculations and for estimating the residual error in the calculations. Calculations on selected diatomic and triatomic systems will be used to illustrate the accuracy that currently can be achieved for molecular systems. In particular, the F + H2 yields HF + H potential energy hypersurface is used to illustrate the impact of these computational advances on the calculation of potential energy surfaces.

Recent advances in electronic structure theory and their influence on the accuracy of ab initio potential energy surfaces

NASA Technical Reports Server (NTRS)

Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Taylor, Peter R.

1988-01-01

Recent advances in electronic structure theory and the availability of high speed vector processors have substantially increased the accuracy of ab initio potential energy surfaces. The recently developed atomic natural orbital approach for basis set contraction has reduced both the basis set incompleteness and superposition errors in molecular calculations. Furthermore, full CI calculations can often be used to calibrate a CASSCF/MRCI approach that quantitatively accounts for the valence correlation energy. These computational advances also provide a vehicle for systematically improving the calculations and for estimating the residual error in the calculations. Calculations on selected diatomic and triatomic systems will be used to illustrate the accuracy that currently can be achieved for molecular systems. In particular, the F+H2 yields HF+H potential energy hypersurface is used to illustrate the impact of these computational advances on the calculation of potential energy surfaces.

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.

Simulation of energy-dependent electron diffusion processes in the Earth's outer radiation belt

DOE PAGES

Ma, Q.; Li, W.; Thorne, R. M.; ...

2016-04-28

The radial and local diffusion processes induced by various plasma waves govern the highly energetic electron dynamics in the Earth's radiation belts, causing distinct characteristics in electron distributions at various energies. In this study, we present our simulation results of the energetic electron evolution during a geomagnetic storm using the University of California, Los Angeles 3-D diffusion code. Following the plasma sheet electron injections, the electrons at different energy bands detected by the Magnetic Electron Ion Spectrometer (MagEIS) and Relativistic Electron Proton Telescope (REPT) instruments on board the Van Allen Probes exhibit a rapid enhancement followed by a slow diffusivemore » movement in differential energy fluxes, and the radial extent to which electrons can penetrate into depends on energy with closer penetration toward the Earth at lower energies than higher energies. We incorporate radial diffusion, local acceleration, and loss processes due to whistler mode wave observations to perform a 3-D diffusion simulation. Here, our simulation results demonstrate that chorus waves cause electron flux increase by more than 1 order of magnitude during the first 18 h, and the subsequent radial extents of the energetic electrons during the storm recovery phase are determined by the coupled radial diffusion and the pitch angle scattering by EMIC waves and plasmaspheric hiss. The radial diffusion caused by ULF waves and local plasma wave scattering are energy dependent, which lead to the observed electron flux variations with energy dependences. Lastly, this study suggests that plasma wave distributions in the inner magnetosphere are crucial for the energy-dependent intrusions of several hundred keV to several MeV electrons.« less

Low-energy electron-impact single ionization of helium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Colgan, J.; Pindzola, M. S.; Childers, G.

2006-04-15

A study is made of low-energy electron-impact single ionization of ground-state helium. The time-dependent close-coupling method is used to calculate total integral, single differential, double differential, and triple differential ionization cross sections for impact electron energies ranging from 32 to 45 eV. For all quantities, the calculated cross sections are found to be in very good agreement with experiment, and for the triple differential cross sections, good agreement is also found with calculations made using the convergent close-coupling technique.

Exploring the interactome: microfluidic isolation of proteins and interacting partners for quantitative analysis by electron microscopy.

PubMed

Giss, Dominic; Kemmerling, Simon; Dandey, Venkata; Stahlberg, Henning; Braun, Thomas

2014-05-20

Multimolecular protein complexes are important for many cellular processes. However, the stochastic nature of the cellular interactome makes the experimental detection of complex protein assemblies difficult and quantitative analysis at the single molecule level essential. Here, we present a fast and simple microfluidic method for (i) the quantitative isolation of endogenous levels of untagged protein complexes from minute volumes of cell lysates under close to physiological conditions and (ii) the labeling of specific components constituting these complexes. The method presented uses specific antibodies that are conjugated via a photocleavable linker to magnetic beads that are trapped in microcapillaries to immobilize the target proteins. Proteins are released by photocleavage, eluted, and subsequently analyzed by quantitative transmission electron microscopy at the single molecule level. Additionally, before photocleavage, immunogold can be employed to label proteins that interact with the primary target protein. Thus, the presented method provides a new way to study the interactome and, in combination with single molecule transmission electron microscopy, to structurally characterize the large, dynamic, heterogeneous multimolecular protein complexes formed.

Intrinsic Resolution of Molecular Electronic Wave Functions and Energies in Terms of Quasi-atoms and Their Interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

West, Aaron C.; Schmidt, Michael W.; Gordon, Mark S.

A general intrinsic energy resolution has been formulated for strongly correlated wave functions in the full molecular valence space and its subspaces. The information regarding the quasi-atomic organization of the molecular electronic structure is extracted from the molecular wave function without introducing any additional postulated model state wave functions. To this end, the molecular wave function is expressed in terms of quasi-atomic molecular orbitals, which maximize the overlap between subspaces of the molecular orbital space and the free-atom orbital spaces. As a result, the molecular wave function becomes the superposition of a wave function representing the non-bonded juxtaposed quasi-atoms andmore » a wave function describing the interatomic electron migrations that create bonds through electron sharing. The juxtaposed nonbonded quasi-atoms are shown to consist of entangled quasi-atomic states from different atoms. The binding energy is resolved as a sum of contributions that are due to quasi-atom formation, quasiclassical electrostatic interactions and interatomic interferences caused by electron sharing. The contributions are further resolved according to orbital interactions. The various transformations that generate the analysis are determined by criteria that are independent of the working orbital basis used for calculating the molecular wave function. Lastly, the theoretical formulation of the resolution is quantitatively validated by an application to the C 2 molecule.« less

Intrinsic Resolution of Molecular Electronic Wave Functions and Energies in Terms of Quasi-atoms and Their Interactions

DOE PAGES

West, Aaron C.; Schmidt, Michael W.; Gordon, Mark S.; ...

2017-01-30

A general intrinsic energy resolution has been formulated for strongly correlated wave functions in the full molecular valence space and its subspaces. The information regarding the quasi-atomic organization of the molecular electronic structure is extracted from the molecular wave function without introducing any additional postulated model state wave functions. To this end, the molecular wave function is expressed in terms of quasi-atomic molecular orbitals, which maximize the overlap between subspaces of the molecular orbital space and the free-atom orbital spaces. As a result, the molecular wave function becomes the superposition of a wave function representing the non-bonded juxtaposed quasi-atoms andmore » a wave function describing the interatomic electron migrations that create bonds through electron sharing. The juxtaposed nonbonded quasi-atoms are shown to consist of entangled quasi-atomic states from different atoms. The binding energy is resolved as a sum of contributions that are due to quasi-atom formation, quasiclassical electrostatic interactions and interatomic interferences caused by electron sharing. The contributions are further resolved according to orbital interactions. The various transformations that generate the analysis are determined by criteria that are independent of the working orbital basis used for calculating the molecular wave function. Lastly, the theoretical formulation of the resolution is quantitatively validated by an application to the C 2 molecule.« less

eV-TEM: Transmission electron microscopy in a low energy cathode lens instrument.

PubMed

Geelen, Daniël; Thete, Aniket; Schaff, Oliver; Kaiser, Alexander; van der Molen, Sense Jan; Tromp, Rudolf

2015-12-01

We are developing a transmission electron microscope that operates at extremely low electron energies, 0-40 eV. We call this technique eV-TEM. Its feasibility is based on the fact that at very low electron energies the number of energy loss pathways decreases. Hence, the electron inelastic mean free path increases dramatically. eV-TEM will enable us to study elastic and inelastic interactions of electrons with thin samples. With the recent development of aberration correction in cathode lens instruments, a spatial resolution of a few nm appears within range, even for these very low electron energies. Such resolution will be highly relevant to study biological samples such as proteins and cell membranes. The low electron energies minimize adverse effects due to radiation damage. Copyright © 2015. Published by Elsevier B.V.

Correlation between energy deposition and molecular damage from Auger electrons: A case study of ultra-low energy (5-18 eV) electron interactions with DNA.

PubMed

Rezaee, Mohammad; Hunting, Darel J; Sanche, Léon

2014-07-01

The present study introduces a new method to establish a direct correlation between biologically related physical parameters (i.e., stopping and damaging cross sections, respectively) for an Auger-electron emitting radionuclide decaying within a target molecule (e.g., DNA), so as to evaluate the efficacy of the radionuclide at the molecular level. These parameters can be applied to the dosimetry of Auger electrons and the quantification of their biological effects, which are the main criteria to assess the therapeutic efficacy of Auger-electron emitting radionuclides. Absorbed dose and stopping cross section for the Auger electrons of 5-18 eV emitted by(125)I within DNA were determined by developing a nanodosimetric model. The molecular damages induced by these Auger electrons were investigated by measuring damaging cross section, including that for the formation of DNA single- and double-strand breaks. Nanoscale films of pure plasmid DNA were prepared via the freeze-drying technique and subsequently irradiated with low-energy electrons at various fluences. The damaging cross sections were determined by employing a molecular survival model to the measured exposure-response curves for induction of DNA strand breaks. For a single decay of(125)I within DNA, the Auger electrons of 5-18 eV deposit the energies of 12.1 and 9.1 eV within a 4.2-nm(3) volume of a hydrated or dry DNA, which results in the absorbed doses of 270 and 210 kGy, respectively. DNA bases have a major contribution to the deposited energies. Ten-electronvolt and high linear energy transfer 100-eV electrons have a similar cross section for the formation of DNA double-strand break, while 100-eV electrons are twice as efficient as 10 eV in the induction of single-strand break. Ultra-low-energy electrons (<18 eV) substantially contribute to the absorbed dose and to the molecular damage from Auger-electron emitting radionuclides; hence, they should be considered in the dosimetry calculation of such

Hilbert transform evaluation for electron-phonon self-energies

NASA Astrophysics Data System (ADS)

Bevilacqua, Giuseppe; Menichetti, Guido; Pastori Parravicini, Giuseppe

2016-01-01

The electron tunneling current through nanostructures is considered in the presence of the electron-phonon interactions. In the Keldysh nonequilibrium formalism, the lesser, greater, advanced and retarded self-energies components are expressed by means of appropriate Langreth rules. We discuss the key role played by the entailed Hilbert transforms, and provide an analytic way for their evaluation. Particular attention is given to the current-conserving lowest-order-expansion for the treament of the electron-phonon interaction; by means of an appropriate elaboration of the analytic properties and pole structure of the Green's functions and of the Fermi functions, we arrive at a surprising simple, elegant, fully analytic and easy-to-use expression of the Hilbert transforms and involved integrals in the energy domain.

Low-energy electron-impact ionization of helium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schow, E.; Hazlett, K.; Childers, J. G.

2005-12-15

Normalized doubly differential cross sections for the electron-impact ionization of helium at low energies are presented. The data are taken at the incident electron energies of 26.3, 28.3, 30.3, 32.5, 34.3, 36.5, and 40.7 eV and for scattering angles of 10 deg. -130 deg. The measurements involve the use of the moveable target method developed at California State University Fullerton to accurately determine the continuum background in the energy-loss spectra. Normalization of experimental data is made on a relative scale to well-established experimental differential cross sections for excitation of the n=2 manifold of helium and then on an absolute scalemore » to the well-established total ionization cross sections of Shah et al. [J. Phys. B 21, 2751 (1988)]. Comparisons are made with available experimental data and the results of the convergent close-coupling theory.« less

Low-dose electron energy-loss spectroscopy using electron counting direct detectors.

PubMed

Maigné, Alan; Wolf, Matthias

2018-03-01

Since the development of parallel electron energy loss spectroscopy (EELS), charge-coupled devices (CCDs) have been the default detectors for EELS. With the recent development of electron-counting direct-detection cameras, micrographs can be acquired under very low electron doses at significantly improved signal-to-noise ratio. In spectroscopy, in particular in combination with a monochromator, the signal can be extremely weak and the detection limit is principally defined by noise introduced by the detector. Here we report the use of an electron-counting direct-detection camera for EEL spectroscopy. We studied the oxygen K edge of amorphous ice and obtained a signal noise ratio up to 10 times higher than with a conventional CCD.We report the application of electron counting to record time-resolved EEL spectra of a biological protein embedded in amorphous ice, revealing chemical changes observed in situ while exposed by the electron beam. A change in the fine structure of nitrogen K and the carbon K edges were recorded during irradiation. A concentration of 3 at% nitrogen was detected with a total electron dose of only 1.7 e-/Å2, extending the boundaries of EELS signal detection at low electron doses.

Speciation of individual mineral particles of micrometer size by the combined use of attenuated total reflectance-Fourier transform-infrared imaging and quantitative energy-dispersive electron probe X-ray microanalysis techniques.

PubMed

Jung, Hae-Jin; Malek, Md Abdul; Ryu, JiYeon; Kim, BoWha; Song, Young-Chul; Kim, HyeKyeong; Ro, Chul-Un

2010-07-15

Our previous work demonstrated for the first time the potential of the combined use of two techniques, attenuated total reflectance FT-IR (ATR-FT-IR) imaging and a quantitative energy-dispersive electron probe X-ray microanalysis, low-Z particle EPMA, for the characterization of individual aerosol particles. In this work, the speciation of mineral particles was performed on a single particle level for 24 mineral samples, including kaolinite, montmorillonite, vermiculite, talc, quartz, feldspar, calcite, gypsum, and apatite, by the combined use of ATR-FT-IR imaging and low-Z particle EPMA techniques. These two single particle analytical techniques provide complementary information, the ATR-FT-IR imaging on mineral types and low-Z particle EPMA on the morphology and elemental concentrations, on the same individual particles. This work demonstrates that the combined use of the two single particle analytical techniques can powerfully characterize externally heterogeneous mineral particle samples in detail and has great potential for the characterization of airborne mineral dust particles.

Enhancement of low-energy electron emission in 2D radioactive films

NASA Astrophysics Data System (ADS)

Pronschinske, Alex; Pedevilla, Philipp; Murphy, Colin J.; Lewis, Emily A.; Lucci, Felicia R.; Brown, Garth; Pappas, George; Michaelides, Angelos; Sykes, E. Charles H.

2015-09-01

High-energy radiation has been used for decades; however, the role of low-energy electrons created during irradiation has only recently begun to be appreciated. Low-energy electrons are the most important component of radiation damage in biological environments because they have subcellular ranges, interact destructively with chemical bonds, and are the most abundant product of ionizing particles in tissue. However, methods for generating them locally without external stimulation do not exist. Here, we synthesize one-atom-thick films of the radioactive isotope 125I on gold that are stable under ambient conditions. Scanning tunnelling microscopy, supported by electronic structure simulations, allows us to directly observe nuclear transmutation of individual 125I atoms into 125Te, and explain the surprising stability of the 2D film as it underwent radioactive decay. The metal interface geometry induces a 600% amplification of low-energy electron emission (<10 eV; ref. ) compared with atomic 125I. This enhancement of biologically active low-energy electrons might offer a new direction for highly targeted nanoparticle therapies.

Nowcast model for low-energy electrons in the inner magnetosphere

NASA Astrophysics Data System (ADS)

Ganushkina, N. Yu.; Amariutei, O. A.; Welling, D.; Heynderickx, D.

2015-01-01

We present the nowcast model for low-energy (<200 keV) electrons in the inner magnetosphere, which is the version of the Inner Magnetosphere Particle Transport and Acceleration Model (IMPTAM) for electrons. Low-energy electron fluxes are very important to specify when hazardous satellite surface-charging phenomena are considered. The presented model provides the low-energy electron flux at all L shells and at all satellite orbits, when necessary. The model is driven by the real-time solar wind and interplanetary magnetic field (IMF) parameters with 1 h time shift for propagation to the Earth's magnetopause and by the real time Dst index. Real-time geostationary GOES 13 or GOES 15 (whenever each is available) data on electron fluxes in three energies, such as 40 keV, 75 keV, and 150 keV, are used for comparison and validation of IMPTAM running online. On average, the model provides quite reasonable agreement with the data; the basic level of the observed fluxes is reproduced. The best agreement between the modeled and the observed fluxes are found for <100 keV electrons. At the same time, not all the peaks and dropouts in the observed electron fluxes are reproduced. For 150 keV electrons, the modeled fluxes are often smaller than the observed ones by an order of magnitude. The normalized root-mean-square deviation is found to range from 0.015 to 0.0324. Though these metrics are buoyed by large standard deviations, owing to the dynamic nature of the fluxes, they demonstrate that IMPTAM, on average, predicts the observed fluxes satisfactorily. The computed binary event tables for predicting high flux values within each 1 h window reveal reasonable hit rates being 0.660-0.318 for flux thresholds of 5 ·104-2 ·105 cm-2 s-1 sr-1 keV-1 for 40 keV electrons, 0.739-0.367 for flux thresholds of 3 ·104-1 ·105 cm-2 s-1 sr-1 keV-1 for 75 keV electrons, and 0.485-0.438 for flux thresholds of 3 ·103-3.5 ·103 cm-2 s-1 sr-1 keV-1 for 150 keV electrons but rather small Heidke

Quantitative structure-activity relationships for reactivities of sulfate and hydroxyl radicals with aromatic contaminants through single-electron transfer pathway.

PubMed

Luo, Shuang; Wei, Zongsu; Spinney, Richard; Villamena, Frederick A; Dionysiou, Dionysios D; Chen, Dong; Tang, Chong-Jian; Chai, Liyuan; Xiao, Ruiyang

2018-02-15

Sulfate radical anion (SO 4 •- ) and hydroxyl radical (OH) based advanced oxidation technologies has been extensively used for removal of aromatic contaminants (ACs) in waters. In this study, we investigated the Gibbs free energy (ΔG SET ∘ ) of the single electron transfer (SET) reactions for 76 ACs with SO 4 •- and OH, respectively. The result reveals that SO 4 •- possesses greater propensity to react with ACs through the SET channel than OH. We hypothesized that the electron distribution within the molecule plays an essential role in determining the ΔG SET ∘ and subsequent SET reactions. To test the hypothesis, a quantitative structure-activity relationship (QSAR) model was developed for predicting ΔG SET ∘ using the highest occupied molecular orbital energies (E HOMO ), a measure of electron distribution and donating ability. The standardized QSAR models are reported to be ΔG ° SET =-0.97×E HOMO - 181 and ΔG ° SET =-0.97×E HOMO - 164 for SO 4 •- and OH, respectively. The models were internally and externally validated to ensure robustness and predictability, and the application domain and limitations were discussed. The single-descriptor based models account for 95% of the variability for SO 4 •- and OH. These results provide the mechanistic insight into the SET reaction pathway of radical and non-radical bimolecular reactions, and have important applications for radical based oxidation technologies to remove target ACs in different waters. Copyright © 2017 Elsevier B.V. All rights reserved.

[Scanning electron microscope observation and image quantitative analysis of Hippocampi].

PubMed

Zhang, Z; Pu, Z; Xu, L; Xu, G; Wang, Q; Xu, G; Wu, L; Chen, J

1998-12-01

The "scale-like projects" on the derma of 3 species of Hippocampi, H. kuda Bleerer, H. trimaculatus Leach and H. japonicus Kaup were observed by scanning electron microscope (SEM). Results showed that some characteristics such us size, shape and type of arrangement of the "scale-like projects" can be considered as the evidence for microanalysis. Image quantitative analysis of the "scale-like project" was carried out on 45 pieces of photograph using area, long diameter, short diameter and shape factor as parameters. No difference among the different parts of the same species was observed, but significant differences were found among the above 3 species.

Low energy electron transport in furfural

NASA Astrophysics Data System (ADS)

Lozano, Ana I.; Krupa, Kateryna; Ferreira da Silva, Filipe; Limão-Vieira, Paulo; Blanco, Francisco; Muñoz, Antonio; Jones, Darryl B.; Brunger, Michael J.; García, Gustavo

2017-09-01

We report on an initial investigation into the transport of electrons through a gas cell containing 1 mTorr of gaseous furfural. Results from our Monte Carlo simulation are implicitly checked against those from a corresponding electron transmission measurement. To enable this simulation a self-consistent cross section data base was constructed. This data base is benchmarked through new total cross section measurements which are also described here. In addition, again to facilitate the simulation, our preferred energy loss distribution function is presented and discussed.

Detectors for low energy electron cooling in RHIC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carlier, F. S.

Low-energy operation of RHIC is of particular interest to study the location of a possible critical point in the QCD phase diagram. The performance of RHIC at energies equal to or lower than 10 GV/nucleon is limited by nonlinearities, Intra-BeamScattering (IBS) processes and space-charge effects. To successfully address the luminosity and ion store lifetime limitations imposed by IBS, the method of electron cooling has been envisaged. During electron cooling processes electrons are injected along with the ion beam at the nominal ion bunch velocities. The velocity spread of the ion beam is reduced in all planes through Coulomb interactions betweenmore » the cold electron beam and the ion beam. The electron cooling system proposed for RHIC will be the first of its kind to use bunched beams for the delivery of the electron bunches, and will therefore be accompanied by the necessary challenges. The designed electron cooler will be located in IP2. The electron bunches will be accelerated by a linac before being injected along side the ion beams. Thirty consecutive electron bunches will be injected to overlap with a single ion bunch. They will first cool the yellow beam before being extracted, turned by 180-degrees, and reinjected into the blue beam for cooling. As such, both the yellow and blue beams will be cooled by the same ion bunches. This will pose considerable challenges to ensure proper electron beam quality to cool the second ion beam. Furthermore, no ondulator will be used in the electron cooler so radiative recombination between the ions and the electrons will occur.« less

Steering continuum electron dynamics by low-energy attosecond streaking

NASA Astrophysics Data System (ADS)

Geng, Ji-Wei; Xiong, Wei-Hao; Xiao, Xiang-Ru; Gong, Qihuang; Peng, Liang-You

2016-08-01

A semiclassical model is developed to understand the electronic dynamics in the low-energy attosecond streaking. Under a relatively strong infrared (IR) pulse, the low-energy part of photoelectrons initialized by a single attosecond pulse (SAP) can either rescatter with the ionic core and induce interferences structures in the momentum spectra of the ionized electrons or be recaptured into the Rydberg states. The Coulomb potential plays essential roles in both the electron rescattering and recapturing processes. We find that by changing the time delay between the SAP and the IR pulse, the photoelectrons yield or the population of the Rydberg states can be effectively controlled. The present study demonstrates a fascinating way to steer the electron motion in the continuum.

Low-energy (<20 eV) and high-energy (1000 eV) electron-induced methanol radiolysis of astrochemical interest

NASA Astrophysics Data System (ADS)

Sullivan, Kristal K.; Boamah, Mavis D.; Shulenberger, Katie E.; Chapman, Sitara; Atkinson, Karen E.; Boyer, Michael C.; Arumainayagam, Christopher R.

2016-07-01

We report the first infrared study of the low-energy (<20 eV) electron-induced reactions of condensed methanol. Our goal is to simulate processes which occur when high-energy cosmic rays interact with interstellar and cometary ices, where methanol, a precursor of several prebiotic species, is relatively abundant. The interactions of high-energy radiation, such as cosmic rays (Emax ˜ 1020 eV), with matter produce large numbers of low-energy secondary electrons, which are known to initiate radiolysis reactions in the condensed phase. Using temperature programmed desorption (TPD) and infrared reflection absorption spectroscopy (IRAS), we have investigated low-energy (5-20 eV) and high-energy (˜1000 eV) electron-induced reactions in condensed methanol (CH3OH). IRAS has the benefit that it does not require thermal processing prior to product detection. Using IRAS, we have found evidence for the formation of ethylene glycol (HOCH2CH2OH), formaldehyde (CH2O), dimethyl ether (CH3OCH3), methane (CH4), carbon dioxide (CO2), carbon monoxide (CO), and the hydroxyl methyl radical (·CH2OH) upon both low-energy and high-energy electron irradiation of condensed methanol at ˜85 K. Additionally, TPD results, presented herein, are similar for methanol films irradiated with both 1000 eV and 20 eV electrons. These IRAS and TPD findings are qualitatively consistent with the hypothesis that high-energy condensed phase radiolysis is mediated by low-energy electron-induced reactions. Moreover, methoxymethanol (CH3OCH2OH) could serve as a tracer molecule for electron-induced reactions in the interstellar medium. The results of experiments such as ours may provide a fundamental understanding of how complex organic molecules are synthesized in cosmic ices.

Quantitative operando visualization of the energy band depth profile in solar cells.

PubMed

Chen, Qi; Mao, Lin; Li, Yaowen; Kong, Tao; Wu, Na; Ma, Changqi; Bai, Sai; Jin, Yizheng; Wu, Dan; Lu, Wei; Wang, Bing; Chen, Liwei

2015-07-13

The energy band alignment in solar cell devices is critically important because it largely governs elementary photovoltaic processes, such as the generation, separation, transport, recombination and collection of charge carriers. Despite the expenditure of considerable effort, the measurement of energy band depth profiles across multiple layers has been extremely challenging, especially for operando devices. Here we present direct visualization of the surface potential depth profile over the cross-sections of operando organic photovoltaic devices using scanning Kelvin probe microscopy. The convolution effect due to finite tip size and cantilever beam crosstalk has previously prohibited quantitative interpretation of scanning Kelvin probe microscopy-measured surface potential depth profiles. We develop a bias voltage-compensation method to address this critical problem and obtain quantitatively accurate measurements of the open-circuit voltage, built-in potential and electrode potential difference.

Drift mobility of photo-electrons in organic molecular crystals: Quantitative comparison between theory and experiment

NASA Astrophysics Data System (ADS)

Reineker, P.; Kenkre, V. M.; Kühne, R.

1981-08-01

A quantitative comparison of a simple theoretical prediction for the drift mobility of photo-electrons in organic molecular crystals, calculated within the model of the coupled band-like and hopping motion, with experiments in napthalene of Schein et al. and Karl et al. is given.

High-energy electron experiments (HEP) aboard the ERG (Arase) satellite

NASA Astrophysics Data System (ADS)

Mitani, Takefumi; Takashima, Takeshi; Kasahara, Satoshi; Miyake, Wataru; Hirahara, Masafumi

2018-05-01

This paper reports the design, calibration, and operation of high-energy electron experiments (HEP) aboard the exploration of energization and radiation in geospace (ERG) satellite. HEP detects 70 keV-2 MeV electrons and generates a three-dimensional velocity distribution for these electrons in every period of the satellite's rotation. Electrons are detected by two instruments, namely HEP-L and HEP-H, which differ in their geometric factor (G-factor) and range of energies they detect. HEP-L detects 70 keV-1 MeV electrons and its G-factor is 9.3 × 10-4 cm2 sr at maximum, while HEP-H observes 0.7-2 MeV electrons and its G-factor is 9.3 × 10-3 cm2 sr at maximum. The instruments utilize silicon strip detectors and application-specific integrated circuits to readout the incident charge signal from each strip. Before the launch, we calibrated the detectors by measuring the energy spectra of all strips using γ-ray sources. To evaluate the overall performance of the HEP instruments, we measured the energy spectra and angular responses with electron beams. After HEP was first put into operation, on February 2, 2017, it was demonstrated that the instruments performed normally. HEP began its exploratory observations with regard to energization and radiation in geospace in late March 2017. The initial results of the in-orbit observations are introduced briefly in this paper.[Figure not available: see fulltext.

Electron energy distributions in uranium helium mixtures. M.S. Thesis

NASA Technical Reports Server (NTRS)

Makowski, M. A.

1977-01-01

The high energy portion of the electron energy distribution for mixtures of uranium and helium at 1 atm, 5000 K, and a neutron flux of 2x10 to the 12th power/sq cm-sec have been calculated. The addition of He improves the heat transport characteristics of the plasma and has the feature that the He energy levels lie in the high energy portion of the electron distribution, potentially allowing non maxwellian excitation. It is concluded, however, that the resulting reaction rates are marginal relative to achieving inversion in He.

Electronic structure of some adenosine receptor antagonists. III. Quantitative investigation of the electronic absorption spectra of alkyl xanthines

NASA Astrophysics Data System (ADS)

Moustafa, H.; Shalaby, Samia H.; El-sawy, K. M.; Hilal, Rifaat

2002-07-01

Quantitative and comparative investigation of the electronic absorption spectra of theophylline, caffeine and their derivatives is reported. The spectra of theophylline, caffeine and theobromine were compared to establish the predominant tautomeric species in solution. This comparison, analysis of solvent effects and assignments of the observed transitions via MO computations indicate the exits of only one tautomeric species in solution that is the N7 form. A low-lying triplet state was identified which corresponds to a HOMO-LUMO transition. This relatively long-lived T 1 state is always less polar than the ground state and may very well underlie the photochemical reactivity of alkyl xanthines. Substituents of different electron donating or withdrawing strengths and solvent effects are investigated and analyzed. The present analysis is facilitated via computer deconvolution of the observed spectra and MO computation.

Low-energy electron scattering from atomic hydrogen. I. Ionization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Childers, J.G.; James, K.E. Jr.; Bray, Igor

2004-02-01

Absolute doubly differential cross sections for the ionization of atomic hydrogen by electron impact have been measured at energies ranging from near threshold to intermediate values. The measurements are normalized to the accurate differential cross section for the electron-impact excitation of the H 1 {sup 2}S{yields}2 {sup 2}S+2 {sup 2}P transition. These measurements were made possible through the use of a moveable target source which enables the collection of hydrogen energy loss spectra free of all backgrounds. The measurements cover the incident electron energy range of 14.6-40 eV and scattering angles from 12 deg. to 127 deg., and are inmore » very good agreement with the results of the latest theoretical models--the convergent close-coupling model and the exterior complex scaling model.« less

Magnetic properties and core electron binding energies of liquid water

NASA Astrophysics Data System (ADS)

Galamba, N.; Cabral, Benedito J. C.

2018-01-01

The magnetic properties and the core and inner valence electron binding energies of liquid water are investigated. The adopted methodology relies on the combination of molecular dynamics and electronic structure calculations. Born-Oppenheimer molecular dynamics with the Becke and Lee-Yang-Parr functionals for exchange and correlation, respectively, and includes an empirical correction (BLYP-D3) functional and classical molecular dynamics with the TIP4P/2005-F model were carried out. The Keal-Tozer functional was applied for predicting magnetic shielding and spin-spin coupling constants. Core and inner valence electron binding energies in liquid water were calculated with symmetry adapted cluster-configuration interaction. The relationship between the magnetic shielding constant σ(17O), the role played by the oxygen atom as a proton acceptor and donor, and the tetrahedral organisation of liquid water are investigated. The results indicate that the deshielding of the oxygen atom in water is very dependent on the order parameter (q) describing the tetrahedral organisation of the hydrogen bond network. The strong sensitivity of magnetic properties on changes of the electronic density in the nuclei environment is illustrated by a correlation between σ(17O) and the energy gap between the 1a1[O1s] (core) and the 2a1 (inner valence) orbitals of water. Although several studies discussed the eventual connection between magnetic properties and core electron binding energies, such a correlation could not be clearly established. Here, we demonstrate that for liquid water this correlation exists although involving the gap between electron binding energies of core and inner valence orbitals.

Quantitative analysis on electric dipole energy in Rashba band splitting.

PubMed

Hong, Jisook; Rhim, Jun-Won; Kim, Changyoung; Ryong Park, Seung; Hoon Shim, Ji

2015-09-01

We report on quantitative comparison between the electric dipole energy and the Rashba band splitting in model systems of Bi and Sb triangular monolayers under a perpendicular electric field. We used both first-principles and tight binding calculations on p-orbitals with spin-orbit coupling. First-principles calculation shows Rashba band splitting in both systems. It also shows asymmetric charge distributions in the Rashba split bands which are induced by the orbital angular momentum. We calculated the electric dipole energies from coupling of the asymmetric charge distribution and external electric field, and compared it to the Rashba splitting. Remarkably, the total split energy is found to come mostly from the difference in the electric dipole energy for both Bi and Sb systems. A perturbative approach for long wave length limit starting from tight binding calculation also supports that the Rashba band splitting originates mostly from the electric dipole energy difference in the strong atomic spin-orbit coupling regime.

Quantitative analysis on electric dipole energy in Rashba band splitting

PubMed Central

Hong, Jisook; Rhim, Jun-Won; Kim, Changyoung; Ryong Park, Seung; Hoon Shim, Ji

2015-01-01

We report on quantitative comparison between the electric dipole energy and the Rashba band splitting in model systems of Bi and Sb triangular monolayers under a perpendicular electric field. We used both first-principles and tight binding calculations on p-orbitals with spin-orbit coupling. First-principles calculation shows Rashba band splitting in both systems. It also shows asymmetric charge distributions in the Rashba split bands which are induced by the orbital angular momentum. We calculated the electric dipole energies from coupling of the asymmetric charge distribution and external electric field, and compared it to the Rashba splitting. Remarkably, the total split energy is found to come mostly from the difference in the electric dipole energy for both Bi and Sb systems. A perturbative approach for long wave length limit starting from tight binding calculation also supports that the Rashba band splitting originates mostly from the electric dipole energy difference in the strong atomic spin-orbit coupling regime. PMID:26323493

Treatment of Electronic Energy Level Transition and Ionization Following the Particle-Based Chemistry Model

NASA Technical Reports Server (NTRS)

Liechty, Derek S.; Lewis, Mark

2010-01-01

A new method of treating electronic energy level transitions as well as linking ionization to electronic energy levels is proposed following the particle-based chemistry model of Bird. Although the use of electronic energy levels and ionization reactions in DSMC are not new ideas, the current method of selecting what level to transition to, how to reproduce transition rates, and the linking of the electronic energy levels to ionization are, to the author s knowledge, novel concepts. The resulting equilibrium temperatures are shown to remain constant, and the electronic energy level distributions are shown to reproduce the Boltzmann distribution. The electronic energy level transition rates and ionization rates due to electron impacts are shown to reproduce theoretical and measured rates. The rates due to heavy particle impacts, while not as favorable as the electron impact rates, compare favorably to values from the literature. Thus, these new extensions to the particle-based chemistry model of Bird provide an accurate method for predicting electronic energy level transition and ionization rates in gases.

Determining the static electronic and vibrational energy correlations via two-dimensional electronic-vibrational spectroscopy

DOE PAGES

Dong, Hui; Lewis, Nicholas H. C.; Oliver, Thomas A. A.; ...

2015-05-07

Changes in the electronic structure of pigments in protein environments and of polar molecules in solution inevitably induce a re-adaption of molecular nuclear structure. Both changes of electronic and vibrational energies can be probed with visible or infrared lasers, such as two-dimensional electronic spectroscopy or vibrational spectroscopy. The extent to which the two changes are correlated remains elusive. The recent demonstration of two-dimensional electronic-vibrational (2DEV) spectroscopy potentially enables a direct measurement of this correlation experimentally. However, it has hitherto been unclear how to characterize the correlation from the spectra. In this report, we present a theoretical formalism to demonstrate themore » slope of the nodal line between the excited state absorption and ground state bleach peaks in the spectra as a characterization of the correlation between electronic and vibrational transition energies. In conclusion, we also show the dynamics of the nodal line slope is correlated to the vibrational spectral dynamics. Additionally, we demonstrate the fundamental 2DEV spectral line-shape of a monomer with newly developed response functions« less

Determining the static electronic and vibrational energy correlations via two-dimensional electronic-vibrational spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Hui; Lewis, Nicholas H. C.; Oliver, Thomas A. A.

2015-05-07

Changes in the electronic structure of pigments in protein environments and of polar molecules in solution inevitably induce a re-adaption of molecular nuclear structure. Both changes of electronic and vibrational energies can be probed with visible or infrared lasers, such as two-dimensional electronic spectroscopy or vibrational spectroscopy. The extent to which the two changes are correlated remains elusive. The recent demonstration of two-dimensional electronic-vibrational (2DEV) spectroscopy potentially enables a direct measurement of this correlation experimentally. However, it has hitherto been unclear how to characterize the correlation from the spectra. In this paper, we present a theoretical formalism to demonstrate themore » slope of the nodal line between the excited state absorption and ground state bleach peaks in the spectra as a characterization of the correlation between electronic and vibrational transition energies. We also show the dynamics of the nodal line slope is correlated to the vibrational spectral dynamics. Additionally, we demonstrate the fundamental 2DEV spectral line-shape of a monomer with newly developed response functions.« less

An electronic portfolio for quantitative assessment of surgical skills in undergraduate medical education.

PubMed

Sánchez Gómez, Serafín; Ostos, Elisa María Cabot; Solano, Juan Manuel Maza; Salado, Tomás Francisco Herrero

2013-05-06

We evaluated a newly designed electronic portfolio (e-Portfolio) that provided quantitative evaluation of surgical skills. Medical students at the University of Seville used the e-Portfolio on a voluntary basis for evaluation of their performance in undergraduate surgical subjects. Our new web-based e-Portfolio was designed to evaluate surgical practical knowledge and skills targets. Students recorded each activity on a form, attached evidence, and added their reflections. Students self-assessed their practical knowledge using qualitative criteria (yes/no), and graded their skills according to complexity (basic/advanced) and participation (observer/assistant/independent). A numerical value was assigned to each activity, and the values of all activities were summated to obtain the total score. The application automatically displayed quantitative feedback. We performed qualitative evaluation of the perceived usefulness of the e-Portfolio and quantitative evaluation of the targets achieved. Thirty-seven of 112 students (33%) used the e-Portfolio, of which 87% reported that they understood the methodology of the portfolio. All students reported an improved understanding of their learning objectives resulting from the numerical visualization of progress, all students reported that the quantitative feedback encouraged their learning, and 79% of students felt that their teachers were more available because they were using the e-Portfolio. Only 51.3% of students reported that the reflective aspects of learning were useful. Individual students achieved a maximum of 65% of the total targets and 87% of the skills targets. The mean total score was 345 ± 38 points. For basic skills, 92% of students achieved the maximum score for participation as an independent operator, and all achieved the maximum scores for participation as an observer and assistant. For complex skills, 62% of students achieved the maximum score for participation as an independent operator, and 98% achieved

Cornell-BNL Electron Energy Recovery Linac FFAG Test Accelerator (CBETA)

NASA Astrophysics Data System (ADS)

Trbojevic, Dejan; Peggs, Steve; Berg, Scott; Brooks, Stephen; Mahler, George; Meot, Francois; Tsoupas, Nicholaos; Witte, Holger; Hoffstaetter, Georg; Bazarov, Ivan; Mayes, Christopher; Patterson, Ritchie; Smolenski, Karl; Li, Yulin; Dobbins, John; BNL Team; Cornell University Team

A novel energy recovery linac (ERL) with Non-Scaling Fixed Field Alternating Gradient (NS-FFAG) racetrack is being constructed as a result of collaboration of the Cornell University with Brookhaven National Laboratory. The existing injector and superconducting linac at Cornell University are being installed together with a single NS-FFAG arcs and straight section at the opposite side of the linac to form an ERL system. The 6 MeV electron beam from injector is transferred into the 36 MeV superconducting linac and accelerated by four successive passes: from 42 to 150 MeV using the same NS-FFAG structure made of permanent magnets. After the maximum energy of 150 MeV is reached, the electron beam is brought back to the linac with opposite Radio Frequency (RF) phase and with 4 passes electron energy is recovered and brought back to the initial energy of 6 MeV. This is going to be the first 4 pass superconducting ERL and the first NS-FFAG permanent magnet structure to bring the electron beam back to the linac.

Dose limited reliability of quantitative annular dark field scanning transmission electron microscopy for nano-particle atom-counting.

PubMed

De Backer, A; Martinez, G T; MacArthur, K E; Jones, L; Béché, A; Nellist, P D; Van Aert, S

2015-04-01

Quantitative annular dark field scanning transmission electron microscopy (ADF STEM) has become a powerful technique to characterise nano-particles on an atomic scale. Because of their limited size and beam sensitivity, the atomic structure of such particles may become extremely challenging to determine. Therefore keeping the incoming electron dose to a minimum is important. However, this may reduce the reliability of quantitative ADF STEM which will here be demonstrated for nano-particle atom-counting. Based on experimental ADF STEM images of a real industrial catalyst, we discuss the limits for counting the number of atoms in a projected atomic column with single atom sensitivity. We diagnose these limits by combining a thorough statistical method and detailed image simulations. Copyright © 2014 Elsevier B.V. All rights reserved.

Quantitative Determination of Spring Water Quality Parameters via Electronic Tongue.

PubMed

Carbó, Noèlia; López Carrero, Javier; Garcia-Castillo, F Javier; Tormos, Isabel; Olivas, Estela; Folch, Elisa; Alcañiz Fillol, Miguel; Soto, Juan; Martínez-Máñez, Ramón; Martínez-Bisbal, M Carmen

2017-12-25

The use of a voltammetric electronic tongue for the quantitative analysis of quality parameters in spring water is proposed here. The electronic voltammetric tongue consisted of a set of four noble electrodes (iridium, rhodium, platinum, and gold) housed inside a stainless steel cylinder. These noble metals have a high durability and are not demanding for maintenance, features required for the development of future automated equipment. A pulse voltammetry study was conducted in 83 spring water samples to determine concentrations of nitrate (range: 6.9-115 mg/L), sulfate (32-472 mg/L), fluoride (0.08-0.26 mg/L), chloride (17-190 mg/L), and sodium (11-94 mg/L) as well as pH (7.3-7.8). These parameters were also determined by routine analytical methods in spring water samples. A partial least squares (PLS) analysis was run to obtain a model to predict these parameter. Orthogonal signal correction (OSC) was applied in the preprocessing step. Calibration (67%) and validation (33%) sets were selected randomly. The electronic tongue showed good predictive power to determine the concentrations of nitrate, sulfate, chloride, and sodium as well as pH and displayed a lower R² and slope in the validation set for fluoride. Nitrate and fluoride concentrations were estimated with errors lower than 15%, whereas chloride, sulfate, and sodium concentrations as well as pH were estimated with errors below 10%.

Estimating the electron energy distribution during ionospheric modification from spectrographic airglow measurements

NASA Astrophysics Data System (ADS)

Hysell, D. L.; Varney, R. H.; Vlasov, M. N.; Nossa, E.; Watkins, B.; Pedersen, T.; Huba, J. D.

2012-02-01

The electron energy distribution during an F region ionospheric modification experiment at the HAARP facility near Gakona, Alaska, is inferred from spectrographic airglow emission data. Emission lines at 630.0, 557.7, and 844.6 nm are considered along with the absence of detectable emissions at 427.8 nm. Estimating the electron energy distribution function from the airglow data is a problem in classical linear inverse theory. We describe an augmented version of the method of Backus and Gilbert which we use to invert the data. The method optimizes the model resolution, the precision of the mapping between the actual electron energy distribution and its estimate. Here, the method has also been augmented so as to limit the model prediction error. Model estimates of the suprathermal electron energy distribution versus energy and altitude are incorporated in the inverse problem formulation as representer functions. Our methodology indicates a heater-induced electron energy distribution with a broad peak near 5 eV that decreases approximately exponentially by 30 dB between 5-50 eV.

Electronic structure and electron energy-loss spectroscopy of ZrO2 zirconia

NASA Astrophysics Data System (ADS)

Dash, L. K.; Vast, Nathalie; Baranek, Philippe; Cheynet, Marie-Claude; Reining, Lucia

2004-12-01

The atomic and electronic structures of zirconia are calculated within density functional theory, and their evolution is analyzed as the crystal-field symmetry changes from tetrahedral [cubic (c-ZrO2) and tetragonal (t-ZrO2) phases] to octahedral (hypothetical rutile ZrO2 ), to a mixing of these symmetries (monoclinic phase, m-ZrO2 ). We find that the theoretical bulk modulus in c-ZrO2 is 30% larger than the experimental value, showing that the introduction of yttria in zirconia has a significant effect. Electronic structure fingerprints which characterize each phase from their electronic spectra are identified. We have carried out electron energy-loss spectroscopy experiments at low momentum transfer and compared these results to the theoretical spectra calculated within the random phase approximation. We show a dependence of the valence and 4p ( N2,3 edge) plasmons on the crystal structure, the dependence of the latter being brought into the spectra by local-field effects. Last, we attribute low energy excitations observed in EELS of m-ZrO2 to defect states 2eV above the top of the intrinsic valence band, and the EELS fundamental band gap value is reconciled with the 5.2 or 5.8eV gaps determined by vacuum ultraviolet spectroscopy.

Suprathermal plasma analyzer for the measurement of low-energy electron distribution in the ionosphere.

PubMed

Shimoyama, M; Oyama, K-I; Abe, T; Yau, A W

2011-07-01

It is commonly believed that an energy transfer from thermal to suprathermal electrons (energy budget of the ionosphere. However, observation of electron energy spectrum in this energy range is quite limited because of technical difficulties of measurement. We have developed an instrument to measure electron energy distribution from thermal to suprathermal energy continuously with high-energy resolution of about 0.15 eV. The measurement principle is based on the combination of a retarding potential analyzer with a channel electron multiplier (CEM) and the Druyvesteyn method, which derives energy distribution from the current-voltage characteristics. The capability of detecting plasma space potential enables absolute calibration of electron energy. The instrument with a small vacuum pump, which is required for the CEM to work in low-vacuum region, was first successfully tested by a sounding rocket S-310-37 in the ionospheric E region. The instrument is expected to provide new opportunities to measure energy distribution of thermal and non-thermal electrons in low-density plasma, where a Langmuir probe cannot measure electron temperature because of low plasma density.

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

Observation of collisionless heating of low energy electrons in low pressure inductively coupled argon plasmas

NASA Astrophysics Data System (ADS)

Lee, Min-Hyong; Lee, Hyo-Chang; Chung, Chin-Wook

2008-12-01

Collisionless heating of low energy electrons was observed in low pressure argon rf-biased inductively coupled plasmas (ICPs) by measurement of the electron energy distribution function (EEDF). When only capacitive power (bias) was supplied, the EEDF in the discharge was a bi-Maxwellian distribution with two electron groups. It was found that the low energy electrons were heated up significantly even with a little inductive power (<20 W) even when the discharge was in E mode. Due to the low gas pressure and low temperature of low energy electrons (close to the energy of the Ramsauer minimum), the collisional heating of low energy electrons appears to be negligible. Therefore, this effective heating of the low energy electrons showed a direct experimental evidence of the collisionless heating by inductive field. The significant heating of low energy electrons in E mode indicates that collisionless heating in the skin layer is an important electron heating mechanism of low pressure ICP even when the discharge is in E mode.

Quantitative operando visualization of the energy band depth profile in solar cells

PubMed Central

Chen, Qi; Mao, Lin; Li, Yaowen; Kong, Tao; Wu, Na; Ma, Changqi; Bai, Sai; Jin, Yizheng; Wu, Dan; Lu, Wei; Wang, Bing; Chen, Liwei

2015-01-01

The energy band alignment in solar cell devices is critically important because it largely governs elementary photovoltaic processes, such as the generation, separation, transport, recombination and collection of charge carriers. Despite the expenditure of considerable effort, the measurement of energy band depth profiles across multiple layers has been extremely challenging, especially for operando devices. Here we present direct visualization of the surface potential depth profile over the cross-sections of operando organic photovoltaic devices using scanning Kelvin probe microscopy. The convolution effect due to finite tip size and cantilever beam crosstalk has previously prohibited quantitative interpretation of scanning Kelvin probe microscopy-measured surface potential depth profiles. We develop a bias voltage-compensation method to address this critical problem and obtain quantitatively accurate measurements of the open-circuit voltage, built-in potential and electrode potential difference. PMID:26166580

Electron detachment energies in high-symmetry alkali halide solvated-electron anions

NASA Astrophysics Data System (ADS)

Anusiewicz, Iwona; Berdys, Joanna; Simons, Jack; Skurski, Piotr

2003-07-01

We decompose the vertical electron detachment energies (VDEs) in solvated-electron clusters of alkali halides in terms of (i) an electrostatic contribution that correlates with the dipole moment (μ) of the individual alkali halide molecule and (ii) a relaxation component that is related to the polarizability (α) of the alkali halide molecule. Detailed numerical ab initio results for twelve species (MX)n- (M=Li,Na; X=F,Cl,Br; n=2,3) are used to construct an interpolation model that relates the clusters' VDEs to their μ and α values as well as a cluster size parameter r that we show is closely related to the alkali cation's ionic radius. The interpolation formula is then tested by applying it to predict the VDEs of four systems [i.e., (KF)2-, (KF)3-, (KCl)2-, and (KCl)3-] that were not used in determining the parameters of the model. The average difference between the model's predicted VDEs and the ab initio calculated electron binding energies is less than 4% (for the twelve species studied). It is concluded that one can easily estimate the VDE of a given high-symmetry solvated electron system by employing the model put forth here if the α, μ and cation ionic radii are known. Alternatively, if VDEs are measured for an alkali halide cluster and the α and μ values are known, one can estimate the r parameter, which, in turn, determines the "size" of the cluster anion.

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.

The role of low-energy electrons in focused electron beam induced deposition: four case studies of representative precursors

PubMed Central

Thorman, Rachel M; Kumar T. P., Ragesh; Fairbrother, D Howard

2015-01-01

Summary Focused electron beam induced deposition (FEBID) is a single-step, direct-write nanofabrication technique capable of writing three-dimensional metal-containing nanoscale structures on surfaces using electron-induced reactions of organometallic precursors. Currently FEBID is, however, limited in resolution due to deposition outside the area of the primary electron beam and in metal purity due to incomplete precursor decomposition. Both limitations are likely in part caused by reactions of precursor molecules with low-energy (<100 eV) secondary electrons generated by interactions of the primary beam with the substrate. These low-energy electrons are abundant both inside and outside the area of the primary electron beam and are associated with reactions causing incomplete ligand dissociation from FEBID precursors. As it is not possible to directly study the effects of secondary electrons in situ in FEBID, other means must be used to elucidate their role. In this context, gas phase studies can obtain well-resolved information on low-energy electron-induced reactions with FEBID precursors by studying isolated molecules interacting with single electrons of well-defined energy. In contrast, ultra-high vacuum surface studies on adsorbed precursor molecules can provide information on surface speciation and identify species desorbing from a substrate during electron irradiation under conditions more representative of FEBID. Comparing gas phase and surface science studies allows for insight into the primary deposition mechanisms for individual precursors; ideally, this information can be used to design future FEBID precursors and optimize deposition conditions. In this review, we give a summary of different low-energy electron-induced fragmentation processes that can be initiated by the secondary electrons generated in FEBID, specifically, dissociative electron attachment, dissociative ionization, neutral dissociation, and dipolar dissociation, emphasizing the

The role of low-energy electrons in focused electron beam induced deposition: four case studies of representative precursors.

PubMed

Thorman, Rachel M; Kumar T P, Ragesh; Fairbrother, D Howard; Ingólfsson, Oddur

2015-01-01

Focused electron beam induced deposition (FEBID) is a single-step, direct-write nanofabrication technique capable of writing three-dimensional metal-containing nanoscale structures on surfaces using electron-induced reactions of organometallic precursors. Currently FEBID is, however, limited in resolution due to deposition outside the area of the primary electron beam and in metal purity due to incomplete precursor decomposition. Both limitations are likely in part caused by reactions of precursor molecules with low-energy (<100 eV) secondary electrons generated by interactions of the primary beam with the substrate. These low-energy electrons are abundant both inside and outside the area of the primary electron beam and are associated with reactions causing incomplete ligand dissociation from FEBID precursors. As it is not possible to directly study the effects of secondary electrons in situ in FEBID, other means must be used to elucidate their role. In this context, gas phase studies can obtain well-resolved information on low-energy electron-induced reactions with FEBID precursors by studying isolated molecules interacting with single electrons of well-defined energy. In contrast, ultra-high vacuum surface studies on adsorbed precursor molecules can provide information on surface speciation and identify species desorbing from a substrate during electron irradiation under conditions more representative of FEBID. Comparing gas phase and surface science studies allows for insight into the primary deposition mechanisms for individual precursors; ideally, this information can be used to design future FEBID precursors and optimize deposition conditions. In this review, we give a summary of different low-energy electron-induced fragmentation processes that can be initiated by the secondary electrons generated in FEBID, specifically, dissociative electron attachment, dissociative ionization, neutral dissociation, and dipolar dissociation, emphasizing the different

Nonequilibrium distribution functions in electron transport: decoherence, energy redistribution and dissipation

NASA Astrophysics Data System (ADS)

Stegmann, Thomas; Ujsághy, Orsolya; Wolf, Dietrich E.

2018-04-01

A new statistical model for the combined effects of decoherence, energy redistribution and dissipation on electron transport in large quantum systems is introduced. The essential idea is to consider the electron phase information to be lost only at randomly chosen regions with an average distance corresponding to the decoherence length. In these regions the electron's energy can be unchanged or redistributed within the electron system or dissipated to a heat bath. The different types of scattering and the decoherence leave distinct fingerprints in the energy distribution functions. They can be interpreted as a mixture of unthermalized and thermalized electrons. In the case of weak decoherence, the fraction of thermalized electrons show electrical and thermal contact resistances. In the regime of incoherent transport the proposed model is equivalent to a Boltzmann equation. The model is applied to experiments with carbon nanotubes. The excellent agreement of the model with the experimental data allows to determine the scattering lengths of the system.

Two-dimensional Electronic Double-Quantum Coherence Spectroscopy

PubMed Central

Kim, Jeongho; Mukamel, Shaul

2009-01-01

CONSPECTUS The theory of electronic structure of many-electron systems like molecules is extraordinarily complicated. A lot can be learned by considering how electron density is distributed, on average, in the average field of the other electrons in the system. That is, mean field theory. However, to describe quantitatively chemical bonds, reactions, and spectroscopy requires consideration of the way that electrons avoid each other by the way they move; this is called electron correlation (or in physics, the many-body problem for fermions). While great progress has been made in theory, there is a need for incisive experimental tests that can be undertaken for large molecular systems in the condensed phase. Here we report a two-dimensional (2D) optical coherent spectroscopy that correlates the double excited electronic states to constituent single excited states. The technique, termed two-dimensional double-coherence spectroscopy (2D-DQCS), makes use of multiple, time-ordered ultrashort coherent optical pulses to create double- and single-quantum coherences over time intervals between the pulses. The resulting two-dimensional electronic spectrum maps the energy correlation between the first excited state and two-photon allowed double-quantum states. The principle of the experiment is that when the energy of the double-quantum state, viewed in simple models as a double HOMO to LUMO excitation, equals twice that of a single excitation, then no signal is radiated. However, electron-electron interactions—a combination of exchange interactions and electron correlation—in real systems generates a signal that reveals precisely how the energy of the double-quantum resonance differs from twice the single-quantum resonance. The energy shift measured in this experiment reveals how the second excitation is perturbed by both the presence of the first excitation and the way that the other electrons in the system have responded to the presence of that first excitation. We

A simple method for electron energy constancy measurement

PubMed Central

King, R. Paul; Anderson, R. Scott

2001-01-01

A device is described for use in confirming the energy constancy of clinical electron beams. A wedge shaped absorber is placed over an ionization chamber leading to an energy dependent response. A measurement under the energy filter is divided by a measurement in air to correct for the inherent energy dependence of the chamber. A nearly linear response is demonstrated. PACS number(s): 87.52.–g, 87.53.–j, 87.66.–a PMID:11674838

High Energy Electron and Gamma - Ray Detection with ATIC

NASA Technical Reports Server (NTRS)

Chang, J.; Schmidt, W. K. H.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

The Advanced Thin Ionization Calorimeter (ATIC) balloon borne ionization calorimeter is well suited to record and identify high energy cosmic ray electrons, and at very high energies gamma-ray photons as well. We have simulated the performance of the instrument, and compare the simulations with actual high energy electron exposures at the CERN accelerator. Simulations and measurements do not compare exactly, in detail, but overall the simulations have predicted actual measured behavior quite well. ATIC has had its first 16 day balloon flight at the turn of the year over Antarctica, and first results obtained using the analysis methods derived from simulations and calibrations will be reported.

Experimental and theoretical triple differential cross sections for electron-impact ionization of Ar (3p) for equal energy final state electrons

NASA Astrophysics Data System (ADS)

Amami, Sadek; Ozer, Zehra N.; Dogan, Mevlut; Yavuz, Murat; Varol, Onur; Madison, Don

2016-09-01

There have been several studies of electron-impact ionization of inert gases for asymmetric final state energy sharing and normally one electron has an energy significantly higher than the other. However, there have been relatively few studies examining equal energy final state electrons. Here we report experimental and theoretical triple differential cross sections for electron impact ionization of Ar (3p) for equal energy sharing of the outgoing electrons. Previous experimental results combined with some new measurements are compared with distorted wave born approximation (DWBA) results, DWBA results using the Ward-Macek (WM) approximation for the post collision interaction (PCI), and three-body distorted wave (3DW) which includes PCI without approximation. The results show that it is crucially important to include PCI in the calculation particularly for lower energies and that the WM approximation is valid only for high energies. The 3DW, on the other hand, is in reasonably good agreement with data down to fairly low energies.

Energy dependence of the spatial distribution of inelastically scattered electrons in backscatter electron diffraction

NASA Astrophysics Data System (ADS)

Ram, Farangis; De Graef, Marc

2018-04-01

In an electron backscatter diffraction pattern (EBSP), the angular distribution of backscattered electrons (BSEs) depends on their energy. Monte Carlo modeling of their depth and energy distributions suggests that the highest energy BSEs are more likely to hit the bottom of the detector than the top. In this paper, we examine experimental EBSPs to validate the modeled angular BSE distribution. To that end, the Kikuchi bandlet method is employed to measure the width of Kikuchi bands in both modeled and measured EBSPs. The results show that in an EBSP obtained with a 15 keV primary probe, the width of a Kikuchi band varies by about 0 .4∘ from the bottom of the EBSD detector to its top. The same is true for a simulated pattern that is composed of BSEs with 5 keV to 15 keV energies, which validates the Monte Carlo simulations.

Precision shape modification of nanodevices with a low-energy electron beam

DOEpatents

Zettl, Alex; Yuzvinsky, Thomas David; Fennimore, Adam

2010-03-09

Methods of shape modifying a nanodevice by contacting it with a low-energy focused electron beam are disclosed here. In one embodiment, a nanodevice may be permanently reformed to a different geometry through an application of a deforming force and a low-energy focused electron beam. With the addition of an assist gas, material may be removed from the nanodevice through application of the low-energy focused electron beam. The independent methods of shape modification and material removal may be used either individually or simultaneously. Precision cuts with accuracies as high as 10 nm may be achieved through the use of precision low-energy Scanning Electron Microscope scan beams. These methods may be used in an automated system to produce nanodevices of very precise dimensions. These methods may be used to produce nanodevices of carbon-based, silicon-based, or other compositions by varying the assist gas.

Electronic energy transfer through non-adiabatic vibrational-electronic resonance. I. Theory for a dimer

NASA Astrophysics Data System (ADS)

Tiwari, Vivek; Peters, William K.; Jonas, David M.

2017-10-01

Non-adiabatic vibrational-electronic resonance in the excited electronic states of natural photosynthetic antennas drastically alters the adiabatic framework, in which electronic energy transfer has been conventionally studied, and suggests the possibility of exploiting non-adiabatic dynamics for directed energy transfer. Here, a generalized dimer model incorporates asymmetries between pigments, coupling to the environment, and the doubly excited state relevant for nonlinear spectroscopy. For this generalized dimer model, the vibrational tuning vector that drives energy transfer is derived and connected to decoherence between singly excited states. A correlation vector is connected to decoherence between the ground state and the doubly excited state. Optical decoherence between the ground and singly excited states involves linear combinations of the correlation and tuning vectors. Excitonic coupling modifies the tuning vector. The correlation and tuning vectors are not always orthogonal, and both can be asymmetric under pigment exchange, which affects energy transfer. For equal pigment vibrational frequencies, the nonadiabatic tuning vector becomes an anti-correlated delocalized linear combination of intramolecular vibrations of the two pigments, and the nonadiabatic energy transfer dynamics become separable. With exchange symmetry, the correlation and tuning vectors become delocalized intramolecular vibrations that are symmetric and antisymmetric under pigment exchange. Diabatic criteria for vibrational-excitonic resonance demonstrate that anti-correlated vibrations increase the range and speed of vibronically resonant energy transfer (the Golden Rule rate is a factor of 2 faster). A partial trace analysis shows that vibronic decoherence for a vibrational-excitonic resonance between two excitons is slower than their purely excitonic decoherence.

Electronic energy transfer through non-adiabatic vibrational-electronic resonance. I. Theory for a dimer.

PubMed

Tiwari, Vivek; Peters, William K; Jonas, David M

2017-10-21

Non-adiabatic vibrational-electronic resonance in the excited electronic states of natural photosynthetic antennas drastically alters the adiabatic framework, in which electronic energy transfer has been conventionally studied, and suggests the possibility of exploiting non-adiabatic dynamics for directed energy transfer. Here, a generalized dimer model incorporates asymmetries between pigments, coupling to the environment, and the doubly excited state relevant for nonlinear spectroscopy. For this generalized dimer model, the vibrational tuning vector that drives energy transfer is derived and connected to decoherence between singly excited states. A correlation vector is connected to decoherence between the ground state and the doubly excited state. Optical decoherence between the ground and singly excited states involves linear combinations of the correlation and tuning vectors. Excitonic coupling modifies the tuning vector. The correlation and tuning vectors are not always orthogonal, and both can be asymmetric under pigment exchange, which affects energy transfer. For equal pigment vibrational frequencies, the nonadiabatic tuning vector becomes an anti-correlated delocalized linear combination of intramolecular vibrations of the two pigments, and the nonadiabatic energy transfer dynamics become separable. With exchange symmetry, the correlation and tuning vectors become delocalized intramolecular vibrations that are symmetric and antisymmetric under pigment exchange. Diabatic criteria for vibrational-excitonic resonance demonstrate that anti-correlated vibrations increase the range and speed of vibronically resonant energy transfer (the Golden Rule rate is a factor of 2 faster). A partial trace analysis shows that vibronic decoherence for a vibrational-excitonic resonance between two excitons is slower than their purely excitonic decoherence.

Quantitative analysis of the effect of environmental-scanning electron microscopy on collagenous tissues.

PubMed

Lee, Woowon; Toussaint, Kimani C

2018-05-31

Environmental-scanning electron microscopy (ESEM) is routinely applied to various biological samples due to its ability to maintain a wet environment while imaging; moreover, the technique obviates the need for sample coating. However, there is limited research carried out on electron-beam (e-beam) induced tissue damage resulting from using the ESEM. In this paper, we use quantitative second-harmonic generation (SHG) microscopy to examine the effects of e-beam exposure from the ESEM on collagenous tissue samples prepared as either fixed, frozen, wet or dehydrated. Quantitative SHG analysis of tissues, before and after ESEM e-beam exposure in low-vacuum mode, reveals evidence of cross-linking of collagen fibers, however there are no structural differences observed in fixed tissue. Meanwhile wet-mode ESEM appears to radically alter the structure from a regular fibrous arrangement to a more random fiber orientation. We also confirm that ESEM images of collagenous tissues show higher spatial resolution compared to SHG microscopy, but the relative tradeoff with collagen specificity reduces its effectiveness in quantifying collagen fiber organization. Our work provides insight on both the limitations of the ESEM for tissue imaging, and the potential opportunity to use as a complementary technique when imaging fine features in the non-collagenous regions of tissue samples.

Shielding Requirements for an Energy-Recovery Linac Free Electron Laser

DTIC Science & Technology

2011-12-01

Radiofrequency TLD Thermo Luminescent Dosimeter xviii THIS PAGE INTENTIONALLY LEFT BLANK xix ACKNOWLEDGMENTS I would like to first thank Professor...FOR AN ENERGY- RECOVERY LINAC FREE ELECTRON LASER by Robert E. Peterson December 2011 Thesis Co-Advisors: William B. Colson Keith...COVERED Master’s Thesis 4. TITLE AND SUBTITLE Shielding Requirements for an Energy-Recovery Linac Free Electron Laser 5. FUNDING NUMBERS 6

Comparative dosimetric characterization for different types of detectors in high-energy electron beams

NASA Astrophysics Data System (ADS)

Lee, Chang Yeol; Kim, Woo Chul; Kim, Hun Jeong; Huh, Hyun Do; Park, Seungwoo; Choi, Sang Hyoun; Kim, Kum Bae; Min, Chul Kee; Kim, Seong Hoon; Shin, Dong Oh

2017-02-01

The purpose of this study is to perform a comparison and on analysis of measured dose factor values by using various commercially available high-energy electron beam detectors to measure dose profiles and energy property data. By analyzing the high-energy electron beam data from each detector, we determined the optimal detector for measuring electron beams in clinical applications. The dose linearity, dose-rate dependence, percentage depth dose, and dose profile of each detector were measured to evaluate the dosimetry characteristics of high-energy electron beams. The dose profile and the energy characteristics of high-energy electron beams were found to be different when measured by different detectors. Through comparison with other detectors based on the analyzed data, the microdiamond detector was found to have outstanding dose linearity, a low dose-rate dependency, and a small effective volume. Thus, this detector has outstanding spatial resolution and is the optimal detector for measuring electron beams. Radiation therapy results can be improved and related medical accidents can be prevented by using the procedure developed in this research in clinical practice for all beam detectors when measuring the electron beam dose.

Spatial nonuniformity of electron energy in a microwave atmospheric-pressure microplasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu Liguo; Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621900; Zhang Zhibo

The characteristics of the electron energy in a microwave atmospheric-pressure argon microplasma are investigated by a spatially resolved optical emission spectroscopy. By adding tiny amount of xenon (<1 ppm) as tracer gas into the argon discharge, it is found that the spatial distribution of the electrons with energy >8.3 eV is quite different from that of the electrons with energy >11.5 eV. Spatial distribution of the population ratio between 4p and 5p levels of Ar atom is also determined. Furthermore, with a collisional-radiative model, it is found that the spatial variation of this population ratio is mainly attributed to themore » spatial nonuniformity of the effective electron temperature.« less

Quantitative Estimation of the Electronic Effects of Substituents in Five-membered Nitrogen-containing Aromatic Heterocycles

NASA Astrophysics Data System (ADS)

Lopyrev, Valentin A.; Larina, Ludmila I.; Vakul'skaya, Tamara I.

1986-05-01

Data, characterising quantitatively the effect of substituents on the reactivity and physicochemical properties of five-membered nitrogen-containing heterocyclic compounds, which have accumulated in the literature during the last 15 years, are compiled in the review and discussed. The possibility of applying the Hammett and Jaffe equations in the determination of the direction of transmission of the electronic effects of substituents is analysed and the likely usefulness of this approach to the study of electronic influences by taking into account separately the inductive and resonance constants is demonstrated. The bibliography includes 215 references.

Low-energy-electron scattering by CH3CN

NASA Astrophysics Data System (ADS)

Maioli, Leticia S.; Bettega, Márcio H. F.

2017-12-01

We report integral and differential cross sections for the elastic scattering of low-energy electrons by methyl cyanide (CH3CN), also known as acetonitrile. The cross sections were computed using the Schwinger multichannel method implemented with pseudopotentials. The fixed-nuclei scattering calculations were performed in the static-exchange and static-exchange plus polarization approximations for energies up to 15 eV. In our calculations with polarization effects, we found a π* shape resonance at around 2.22 eV and a broad structure associated to a σ* shape resonance at around 7 eV. The low-lying resonance was assigned to the electron capture by the two-fold degenerate π* orbital of the E symmetry of C3v group; the second was assigned to a σ* shape resonance in the A1 symmetry. We compared our cross sections with theoretical results and experimental data available in the literature, and in general we found good agreement for the positions of the two resonances. Contribution to the Topical Issue: "Low Energy Positron and Electron Interactions", edited by James Sullivan, Ron White, Michael Bromley, Ilya Fabrikant, and David Cassidy.

The Darkside-50 Experiment: Electron Recoil Calibrations and a Global Energy Variable

NASA Astrophysics Data System (ADS)

Hackett, Brianne R.

Over the course of decades, there has been mounting astronomical evidence for non-baryonic dark matter, yet its precise nature remains elusive. A favored candidate for dark matter is the Weakly Interacting Massive Particle (WIMP) which arises naturally out of extensions to the Standard Model. WIMPs are expected to occasionally interact with particles of normal matter through nuclear recoils. DarkSide-50 aims to detect this type of particle through the use of a two-phase liquid argon time projection chamber. To make a claim of discovery, an accurate understanding of the background and WIMP search region is imperative. Knowledge of the backgrounds is done through extensive studies of DarkSide-50's response to electron and nuclear recoils. The CALibration Insertion System (CALIS) was designed and built for the purpose of introducing radioactive sources into or near the detector in a joint effort between Fermi National Laboratory (FNAL) and the University of Hawai'i at Manoa. This work describes the testing, installation, and commissioning of CALIS at the Laboratori Nazionali del Gran Sasso. CALIS has been used in multiple calibration campaigns with both neutron and gamma sources. In this work, DarkSide-50's response to electron recoils, which are important for background estimations, was studied through the use of gamma calibration sources by constructing a global energy variable which takes into account the anti-correlation between scintillation and ionization signals produced by interactions in the liquid argon. Accurately reconstructing the event energy correlates directly with quantitatively understanding the WIMP sensitivity in DarkSide-50. This work also validates the theoretically predicted beta decay spectrum of 39Ar against 39Ar beta decay data collected in the early days of DarkSide-50 while it was filled with atmospheric argon; a validation of this type is not readily found in the literature. Finally, we show how well the constructed energy variable can

Thickness dependence of scattering cross-sections in quantitative scanning transmission electron microscopy.

PubMed

Martinez, G T; van den Bos, K H W; Alania, M; Nellist, P D; Van Aert, S

2018-04-01

In quantitative scanning transmission electron microscopy (STEM), scattering cross-sections have been shown to be very sensitive to the number of atoms in a column and its composition. They correspond to the integrated intensity over the atomic column and they outperform other measures. As compared to atomic column peak intensities, which saturate at a given thickness, scattering cross-sections increase monotonically. A study of the electron wave propagation is presented to explain the sensitivity of the scattering cross-sections. Based on the multislice algorithm, we analyse the wave propagation inside the crystal and its link to the scattered signal for the different probe positions contained in the scattering cross-section for detector collection in the low-, middle- and high-angle regimes. The influence to the signal from scattering of neighbouring columns is also discussed. Copyright © 2018 Elsevier B.V. All rights reserved.

Correlation between energy deposition and molecular damage from Auger electrons: A case study of ultra-low energy (5–18 eV) electron interactions with DNA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rezaee, Mohammad, E-mail: Mohammad.Rezaee@USherbrooke.ca; Hunting, Darel J.; Sanche, Léon

2014-07-15

Purpose: The present study introduces a new method to establish a direct correlation between biologically related physical parameters (i.e., stopping and damaging cross sections, respectively) for an Auger-electron emitting radionuclide decaying within a target molecule (e.g., DNA), so as to evaluate the efficacy of the radionuclide at the molecular level. These parameters can be applied to the dosimetry of Auger electrons and the quantification of their biological effects, which are the main criteria to assess the therapeutic efficacy of Auger-electron emitting radionuclides. Methods: Absorbed dose and stopping cross section for the Auger electrons of 5–18 eV emitted by{sup 125}I withinmore » DNA were determined by developing a nanodosimetric model. The molecular damages induced by these Auger electrons were investigated by measuring damaging cross section, including that for the formation of DNA single- and double-strand breaks. Nanoscale films of pure plasmid DNA were prepared via the freeze-drying technique and subsequently irradiated with low-energy electrons at various fluences. The damaging cross sections were determined by employing a molecular survival model to the measured exposure–response curves for induction of DNA strand breaks. Results: For a single decay of{sup 125}I within DNA, the Auger electrons of 5–18 eV deposit the energies of 12.1 and 9.1 eV within a 4.2-nm{sup 3} volume of a hydrated or dry DNA, which results in the absorbed doses of 270 and 210 kGy, respectively. DNA bases have a major contribution to the deposited energies. Ten-electronvolt and high linear energy transfer 100-eV electrons have a similar cross section for the formation of DNA double-strand break, while 100-eV electrons are twice as efficient as 10 eV in the induction of single-strand break. Conclusions: Ultra-low-energy electrons (<18 eV) substantially contribute to the absorbed dose and to the molecular damage from Auger-electron emitting radionuclides; hence, they

Correlation between energy deposition and molecular damage from Auger electrons: A case study of ultra-low energy (5–18 eV) electron interactions with DNA

PubMed Central

Rezaee, Mohammad; Hunting, Darel J.; Sanche, Léon

2015-01-01

Purpose The present study introduces a new method to establish a direct correlation between biologically related physical parameters (i.e., stopping and damaging cross sections, respectively) for an Auger-electron emitting radionuclide decaying within a target molecule (e.g., DNA), so as to evaluate the efficacy of the radionuclide at the molecular level. These parameters can be applied to the dosimetry of Auger electrons and the quantification of their biological effects, which are the main criteria to assess the therapeutic efficacy of Auger-electron emitting radionuclides. Methods Absorbed dose and stopping cross section for the Auger electrons of 5–18 eV emitted by 125I within DNA were determined by developing a nanodosimetric model. The molecular damages induced by these Auger electrons were investigated by measuring damaging cross section, including that for the formation of DNA single- and double-strand breaks. Nanoscale films of pure plasmid DNA were prepared via the freeze-drying technique and subsequently irradiated with low-energy electrons at various fluences. The damaging cross sections were determined by employing a molecular survival model to the measured exposure–response curves for induction of DNA strand breaks. Results For a single decay of 125I within DNA, the Auger electrons of 5–18 eV deposit the energies of 12.1 and 9.1 eV within a 4.2-nm3 volume of a hydrated or dry DNA, which results in the absorbed doses of 270 and 210 kGy, respectively. DNA bases have a major contribution to the deposited energies. Ten-electronvolt and high linear energy transfer 100-eV electrons have a similar cross section for the formation of DNA double-strand break, while 100-eV electrons are twice as efficient as 10 eV in the induction of single-strand break. Conclusions Ultra-low-energy electrons (<18 eV) substantially contribute to the absorbed dose and to the molecular damage from Auger-electron emitting radionuclides; hence, they should be considered in the

Non-equilibrium thermionic electron emission for metals at high temperatures

NASA Astrophysics Data System (ADS)

Domenech-Garret, J. L.; Tierno, S. P.; Conde, L.

2015-08-01

Stationary thermionic electron emission currents from heated metals are compared against an analytical expression derived using a non-equilibrium quantum kappa energy distribution for the electrons. The latter depends on the temperature decreasing parameter κ ( T ) , which decreases with increasing temperature and can be estimated from raw experimental data and characterizes the departure of the electron energy spectrum from equilibrium Fermi-Dirac statistics. The calculations accurately predict the measured thermionic emission currents for both high and moderate temperature ranges. The Richardson-Dushman law governs electron emission for large values of kappa or equivalently, moderate metal temperatures. The high energy tail in the electron energy distribution function that develops at higher temperatures or lower kappa values increases the emission currents well over the predictions of the classical expression. This also permits the quantitative estimation of the departure of the metal electrons from the equilibrium Fermi-Dirac statistics.

Effects of Energy Chirp on Echo-Enabled Harmonic Generation Free-Electron Lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Z.; Ratner, D.; Stupakov, G.

2009-02-23

We study effects of energy chirp on echo-enabled harmonic generation (EEHG). Analytical expressions are compared with numerical simulations for both harmonic and bunching factors. We also discuss the EEHG free-electron laser bandwidth increase due to an energy-modulated beam and its pulse length dependence on the electron energy chirp.

Auger electron and characteristic energy loss spectra for electro-deposited americium-241

NASA Astrophysics Data System (ADS)

Varma, Matesh N.; Baum, John W.

1983-07-01

Auger electron energy spectra for electro-deposited americium-241 on platinum substrate were obtained using a cylindrical mirror analyzer. Characteristic energy loss spectra for this sample were also obtained at primary electron beam energies of 990 and 390 eV. From these measurements PI, PII, and PIII energy levels for americium-241 are determined. Auger electron energies are compared with theoretically calculated values. Minimum detectability under the present condition of sample preparation and equipment was estimated at approximately 1.2×10-8 g/cm2 or 3.9×10-8 Ci/cm2. Minimum detectability for plutonium-239 under similar conditions was estimated at about 7.2×10-10 Ci/cm2.

Thermo electronic laser energy conversion

NASA Technical Reports Server (NTRS)

Hansen, L. K.; Rasor, N. S.

1976-01-01

The thermo electronic laser energy converter (TELEC) is described and compared to the Waymouth converter and the conventional thermionic converter. The electrical output characteristics and efficiency of TELEC operation are calculated for a variety of design variables. Calculations and results are briefly outlined. It is shown that the TELEC concept can potentially convert 25 to 50 percent of incident laser radiation into electric power at high power densities and high waste heat rejection temperatures.

Ultra-High-Contrast Laser Acceleration of Relativistic Electrons in Solid Targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Higginson, Drew Pitney

2013-01-01

The cone-guided fast ignition approach to Inertial Con nement Fusion requires laser-accelerated relativistic electrons to deposit kilojoules of energy within an imploded fuel core to initiate fusion burn. One obstacle to coupling electron energy into the core is the ablation of material, known as preplasma, by laser energy proceeding nanoseconds prior to the main pulse. This causes the laser-absorption surface to be pushed back hundreds of microns from the initial target surface; thus increasing the distance that electrons must travel to reach the imploded core. Previous experiments have shown an order of magnitude decrease in coupling into surrogate targets whenmore » intentionally increasing the amount of preplasma. Additionally, for electrons to deposit energy within the core, they should have kinetic energies on the order of a few MeV, as less energetic electrons will be stopped prior to the core and more energetic electrons will pass through the core without depositing much energy. Thus a quantitative understanding of the electron energy spectrum and how it responds to varied laser parameters is paramount for fast ignition. For the rst time, this dissertation quantitatively investigates the acceleration of electrons using an ultra-high-contrast laser. Ultra-high-contrast lasers reduce the laser energy that reaches the target prior to the main pulse; drastically reducing the amount of preplasma. Experiments were performed in a cone-wire geometry relevant to fast ignition. These experiments irradiated the inner-tip of a Au cone with the laser and observed electrons that passed through a Cu wire attached to the outer-tip of the cone. The total emission of K x-rays is used as a diagnostic to infer the electron energy coupled into the wire. Imaging the x-ray emission allowed an e ective path-length of electrons within the wire to be determined, which constrained the electron energy spectrum. Experiments were carried out on the ultra-high-contrast Trident laser at

Quantitative Determination of Spring Water Quality Parameters via Electronic Tongue

PubMed Central

Carbó, Noèlia; López Carrero, Javier; Garcia-Castillo, F. Javier; Olivas, Estela; Folch, Elisa; Alcañiz Fillol, Miguel; Soto, Juan

2017-01-01

The use of a voltammetric electronic tongue for the quantitative analysis of quality parameters in spring water is proposed here. The electronic voltammetric tongue consisted of a set of four noble electrodes (iridium, rhodium, platinum, and gold) housed inside a stainless steel cylinder. These noble metals have a high durability and are not demanding for maintenance, features required for the development of future automated equipment. A pulse voltammetry study was conducted in 83 spring water samples to determine concentrations of nitrate (range: 6.9–115 mg/L), sulfate (32–472 mg/L), fluoride (0.08–0.26 mg/L), chloride (17–190 mg/L), and sodium (11–94 mg/L) as well as pH (7.3–7.8). These parameters were also determined by routine analytical methods in spring water samples. A partial least squares (PLS) analysis was run to obtain a model to predict these parameter. Orthogonal signal correction (OSC) was applied in the preprocessing step. Calibration (67%) and validation (33%) sets were selected randomly. The electronic tongue showed good predictive power to determine the concentrations of nitrate, sulfate, chloride, and sodium as well as pH and displayed a lower R2 and slope in the validation set for fluoride. Nitrate and fluoride concentrations were estimated with errors lower than 15%, whereas chloride, sulfate, and sodium concentrations as well as pH were estimated with errors below 10%. PMID:29295592

Radiation Belt Electron Energy Spectra Characterization and Evolution Based on the Van Allen Probes Measurements

NASA Astrophysics Data System (ADS)

Zhao, H.; Baker, D. N.; Jaynes, A. N.; Li, X.; Kanekal, S. G.; Blum, L. W.; Schiller, Q. A.; Leonard, T. W.; Elkington, S. R.

2017-12-01

The electron energy spectra, as an important characteristic of radiation belt electrons, provide valuable information on the physical mechanisms affecting different electron populations. Based on the measurements of 30 keV - 10 MeV electrons from MagEIS and REPT instruments on the Van Allen Probes, case studies and statistical analysis of the radiation belt electron energy spectra characterization and evolution have been performed. Generally the radiation belt electron energy spectra can be represented by one of the three types of distributions: exponential, power law, and bump-on-tail. Statistical analysis shows that the exponential spectra are usually dominant in the outer radiation belt; as the geomagnetic storms occur, energy spectra in the outer belt soften at first due to injection of lower-energy electrons and loss of higher-energy electrons, and gradually get harder due to loss of lower-energy electrons and delayed enhancement of higher energy electron fluxes. Power law spectra generally dominate the inner belt and higher L region (L>6) during injections. Bump-on-tail spectra commonly exist inside the plasmasphere following the geomagnetic storms and/or the compression of plasmasphere, while the energy of flux maxima is usually 1.8 MeV as the bump-on-tail spectra form and gradually moves to higher energies as the spectra evolve, with the ratio of flux maxima to minima up to >10. Detailed event study indicates that the appearance of bump-on-tail spectra are mainly due to energy-dependent losses caused by the plasmaspheric hiss wave scattering, while the disappearance of these spectra can be attributed to fast flux enhancements of lower-energy electrons during storms.

Set-up and demonstration of a Low Energy Electron Magnetometer (LEEM)

NASA Technical Reports Server (NTRS)

Rayborn, G. H.

1986-01-01

Described are the design, construction and test results of a Low Energy Electron Magnetometer (LEEM). The electron source is a commercial electron gun capable of providing several microamperes of electron beam. These electrons, after acceleration through a selected potential difference of 100-300 volts, are sent through two 30 degree second-order focussing parallel plate electrostatic analyzers. The first analyzer acts as a monochromator located in the field-free space. It is capable of providing energy resolution of better than 10 to the -3 power. The second analyzer, located in the test field region, acts as the detector for electrons deflected by the test field. The entire magnetometer system is expected to have a resolution of 1 part in 1000 or better.

Curing Composite Materials Using Lower-Energy Electron Beams

NASA Technical Reports Server (NTRS)

Byrne, Catherine A.; Bykanov, Alexander

2004-01-01

In an improved method of fabricating composite-material structures by laying up prepreg tapes (tapes of fiber reinforcement impregnated by uncured matrix materials) and then curing them, one cures the layups by use of beams of electrons having kinetic energies in the range of 200 to 300 keV. In contrast, in a prior method, one used electron beams characterized by kinetic energies up to 20 MeV. The improved method was first suggested by an Italian group in 1993, but had not been demonstrated until recently. With respect to both the prior method and the present improved method, the impetus for the use of electron- beam curing is a desire to avoid the high costs of autoclaves large enough to effect thermal curing of large composite-material structures. Unfortunately, in the prior method, the advantages of electron-beam curing are offset by the need for special walls and ceilings on curing chambers to shield personnel from x rays generated by impacts of energetic electrons. These shields must be thick [typically 2 to 3 ft (about 0.6 to 0.9 m) if made of concrete] and are therefore expensive. They also make it difficult to bring large structures into and out of the curing chambers. Currently, all major companies that fabricate composite-material spacecraft and aircraft structures form their layups by use of automated tape placement (ATP) machines. In the present improved method, an electron-beam gun is attached to an ATP head and used to irradiate the tape as it is pressed onto the workpiece. The electron kinetic energy between 200 and 300 keV is sufficient for penetration of the ply being laid plus one or two of the plies underneath it. Provided that the electron-beam gun is properly positioned, it is possible to administer the required electron dose and, at the same time, to protect personnel with less shielding than is needed in the prior method. Adequate shielding can be provided by concrete walls 6 ft (approximately equal to 1.8 m) high and 16 in. (approximately

First quantitative measurements of charged-particle stopping and its dependence on electron temperature and density in Inertial-Confinement-Fusion plasmas

NASA Astrophysics Data System (ADS)

Frenje, J.; Li, C. K.; Séguin, F.; Zylstra, A.; Rinderknecht, H.; Petrasso, R.; Delettrez, J.; Glebov, V.; Sangster, T.

2013-10-01

We report on the first quantitative measurements of charged-particle stopping in Inertial-Confinement-Fusion (ICF) plasmas at various conditions. In these experiments, four charged fusion products from the DD and D3He reactions in D3He gas-filled filled implosions were used to determine the stopping power of ICF plasmas at electron temperatures (Te) , ion temperatures (Ti) , and areal densities (ρR) in the range of 0.6-4.0 keV, 3-14 keV and 2-10 mg/cm2, respectively. The resulting data, in the form of measured energy downshift of the charged fusion products, clearly indicate that the stopping-power function depends strongly on Te. It was also observed that the stopping-power function change in characteristics for higher-density implosions in which ions and electrons equilibrate faster, resulting in higher Te relative to Ti and higher ρR s. These results will be modelled by Landau-Spitzer theory and contrasted to different stopping-power models. This work was partially supported by the US DOE, NLUF, LLE, and GA.

s-wave threshold in electron attachment - Observations and cross sections in CCl4 and SF6 at ultralow electron energies

NASA Technical Reports Server (NTRS)

Chutjian, A.; Alajajian, S. H.

1985-01-01

The threshold photoionization method was used to study low-energy electron attachment phenomena in and cross sections of CCl4 and SF6 compounds, which have applications in the design of gaseous dielectrics and diffuse discharge opening switches. Measurements were made at electron energies from below threshold to 140 meV at resolutions of 6 and 8 meV. A narrow resolution-limited structure was observed in electron attachment to CCl4 and SF6 at electron energies below 10 meV, which is attributed to the divergence of the attachment cross section in the limit epsilon, l approaches zero. The results are compared with experimental collisional-ionization results, electron-swarm unfolded cross sections, and earlier threshold photoionization data.

Syringe Injectable Electronics: Precise Targeted Delivery with Quantitative Input/Output Connectivity.

PubMed

Hong, Guosong; Fu, Tian-Ming; Zhou, Tao; Schuhmann, Thomas G; Huang, Jinlin; Lieber, Charles M

2015-10-14

Syringe-injectable mesh electronics with tissue-like mechanical properties and open macroporous structures is an emerging powerful paradigm for mapping and modulating brain activity. Indeed, the ultraflexible macroporous structure has exhibited unprecedented minimal/noninvasiveness and the promotion of attractive interactions with neurons in chronic studies. These same structural features also pose new challenges and opportunities for precise targeted delivery in specific brain regions and quantitative input/output (I/O) connectivity needed for reliable electrical measurements. Here, we describe new results that address in a flexible manner both of these points. First, we have developed a controlled injection approach that maintains the extended mesh structure during the "blind" injection process, while also achieving targeted delivery with ca. 20 μm spatial precision. Optical and microcomputed tomography results from injections into tissue-like hydrogel, ex vivo brain tissue, and in vivo brains validate our basic approach and demonstrate its generality. Second, we present a general strategy to achieve up to 100% multichannel I/O connectivity using an automated conductive ink printing methodology to connect the mesh electronics and a flexible flat cable, which serves as the standard "plug-in" interface to measurement electronics. Studies of resistance versus printed line width were used to identify optimal conditions, and moreover, frequency-dependent noise measurements show that the flexible printing process yields values comparable to commercial flip-chip bonding technology. Our results address two key challenges faced by syringe-injectable electronics and thereby pave the way for facile in vivo applications of injectable mesh electronics as a general and powerful tool for long-term mapping and modulation of brain activity in fundamental neuroscience through therapeutic biomedical studies.

Electron energy deposition in N2 gas

NASA Technical Reports Server (NTRS)

Fox, J. L.; Victor, G. A.

1988-01-01

The processes by which energetic electrons lose energy in a weakly ionized gas of molecular nitrogen are analyzed and calculations are carried out taking into account the discrete nature of the excitation processes. The excitation, ionization, dissociation and heating efficiencies are computed for energies up to 200 eV absorbed in a gas with fractional ionizations varying from 10(-6) to 10(-2). Individual vibrational excitations up to the seventh vibrational level are presented.

Gap length effect on electron energy distribution in capacitive radio frequency discharges

NASA Astrophysics Data System (ADS)

You, S. J.; Kim, S. S.; Kim, Jung-Hyung; Seong, Dae-Jin; Shin, Yong-Hyeon; Chang, H. Y.

2007-11-01

A study on the dependence of electron energy distribution function (EEDF) on discharge gap size in capacitive rf discharges was conducted. The evolution of the EEDF over a gap size range from 2.5to7cm in 65mTorr Ar discharges was investigated both experimentally and theoretically. The measured EEDFs exhibited typical bi-Maxwellian forms with low energy electron groups. A significant depletion in the low energy portion of the bi-Maxwellian was found with decreasing gap size. The results show that electron heating by bulk electric fields, which is the main heating process of the low-energy electrons, is greatly enhanced as the gap size decreases, resulting in the abrupt change of the EEDF. The calculated EEDFs based on nonlocal kinetic theory are in good agreement with the experiments.

Detection of explosives, nerve agents, and illicit substances by zero-energy electron attachment

NASA Technical Reports Server (NTRS)

Chutjian, A.; Darrach, M. R.

2000-01-01

The Reversal Electron Attachment Detection (READ) method, developed at JPL/Caltech, has been used to detect a variety of substances which have electron-attachment resonances at low and intermediate electron energies. In the case of zero-energy resonances, the cross section (hence attachment probability and instrument sensitivity) is mediated by the so-called s-wave phenomenon, in which the cross sections vary as the inverse of the electron velocity. Hence this is, in the limit of zero electron energy or velocity, one of the rare cases in atomic and molecular physics where one carries out detection via infinite cross sections.

Differential cross sections for the electron impact ionization of Ar (3 p) atoms for equal energy final state electrons

NASA Astrophysics Data System (ADS)

Purohit, Ghanshyam; Singh, Prithvi

2017-06-01

The electron-impact ionization of inert gases for asymmetric final state energy sharing conditions has been studied in detail. However, there have been relatively few studies examining equal energy final state electrons. We report in this communication the results of triple differential cross sections (TDCSs) for electron impact ionization of Ar (3 p) for equal energy sharing of the outgoing electrons. We calculate TDCS in the modified distorted wave Born approximation (DWBA) formalism including post collision interaction (PCI) and polarization potential. We compare the results of our calculation with available measurements [Phys. Rev. A 87, 022712 (2013)]. We study the effect of PCI, target polarization on the trends of TDCS for the single ionization of Ar (3 p) targets.

Vibrational and Electronic Energy Transfer and Dissociation of Diatomic Molecules by Electron Collisions

NASA Technical Reports Server (NTRS)

Huo, Winifred M.; Langhoff, Stephen R. (Technical Monitor)

1995-01-01

At high altitudes and velocities equal to or greater than the geosynchronous return velocity (10 kilometers per second), the shock layer of a hypersonic flight will be in thermochemical nonequilibrium and partially ionized. The amount of ionization is determined by the velocity. For a trans atmospheric flight of 10 kilometers per second and at an altitude of 80 kilometers, a maximum of 1% ionization is expected. At a velocity of 12 - 17 kilometer per second, such as a Mars return mission, up to 30% of the atoms and molecules in the flow field will be ionized. Under those circumstances, electrons play an important role in determining the internal states of atoms and molecules in the flow field and hence the amount of radiative heat load and the distance it takes for the flow field to re-establish equilibrium. Electron collisions provide an effective means of transferring energy even when the electron number density is as low as 1%. Because the mass of an electron is 12,760 times smaller than the reduced mass of N2, its average speed, and hence its average collision frequency, is more than 100 times larger. Even in the slightly ionized regime with only 1% electrons, the frequency of electron-molecule collisions is equal to or larger than that of molecule-molecule collisions, an important consideration in the low density part of the atmosphere. Three electron-molecule collision processes relevant to hypersonic flows will be considered: (1) vibrational excitation/de-excitation of a diatomic molecule by electron impact, (2) electronic excitation/de-excitation, and (3) dissociative recombination in electron-diatomic ion collisions. A review of available data, both theory and experiment, will be given. Particular attention will be paid to tailoring the molecular physics to the condition of hypersonic flows. For example, the high rotational temperatures in a hypersonic flow field means that most experimental data carried out under room temperatures are not applicable. Also

Pulsed-field ionization zero electron kinetic energy spectrum of the ground electronic state of BeOBe+.

PubMed

Antonov, Ivan O; Barker, Beau J; Heaven, Michael C

2011-01-28

The ground electronic state of BeOBe(+) was probed using the pulsed-field ionization zero electron kinetic energy photoelectron technique. Spectra were rotationally resolved and transitions to the zero-point level, the symmetric stretch fundamental and first two bending vibrational levels were observed. The rotational state symmetry selection rules confirm that the ground electronic state of the cation is (2)Σ(g)(+). Detachment of an electron from the HOMO of neutral BeOBe results in little change in the vibrational or rotational constants, indicating that this orbital is nonbonding in nature. The ionization energy of BeOBe [65480(4) cm(-1)] was refined over previous measurements. Results from recent theoretical calculations for BeOBe(+) (multireference configuration interaction) were found to be in good agreement with the experimental data.

Ligand reorganization and activation energies in nonadiabatic electron transfer reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu Jianjun; Wang Jianji; Stell, George

2006-10-28

The activation energy and ligand reorganization energy for nonadiabatic electron transfer reactions in chemical and biological systems are investigated in this paper. The free energy surfaces and the activation energy are derived exactly in the general case in which the ligand vibration frequencies are not equal. The activation energy is derived by free energy minimization at the transition state. Our formulation leads to the Marcus-Hush [J. Chem. Phys. 24, 979 (1956); 98, 7170 (1994); 28, 962 (1958)] results in the equal-frequency limit and also generalizes the Marcus-Sumi [J. Chem. Phys. 84, 4894 (1986)] model in the context of studying themore » solvent dynamic effect on electron transfer reactions. It is found that when the ligand vibration frequencies are different, the activation energy derived from the Marcus-Hush formula deviates by 5%-10% from the exact value. If the reduced reorganization energy approximation is introduced in the Marcus-Hush formula, the result is almost exact.« less

Ligand reorganization and activation energies in nonadiabatic electron transfer reactions

NASA Astrophysics Data System (ADS)

Zhu, Jianjun; Wang, Jianji; Stell, George

2006-10-01

The activation energy and ligand reorganization energy for nonadiabatic electron transfer reactions in chemical and biological systems are investigated in this paper. The free energy surfaces and the activation energy are derived exactly in the general case in which the ligand vibration frequencies are not equal. The activation energy is derived by free energy minimization at the transition state. Our formulation leads to the Marcus-Hush [J. Chem. Phys. 24, 979 (1956); 98, 7170 (1994); 28, 962 (1958)] results in the equal-frequency limit and also generalizes the Marcus-Sumi [J. Chem. Phys. 84, 4894 (1986)] model in the context of studying the solvent dynamic effect on electron transfer reactions. It is found that when the ligand vibration frequencies are different, the activation energy derived from the Marcus-Hush formula deviates by 5%-10% from the exact value. If the reduced reorganization energy approximation is introduced in the Marcus-Hush formula, the result is almost exact.

An Overview of Electron-Proton and High Energy Telescopes of Solar Orbiter

NASA Astrophysics Data System (ADS)

Kulkarni, S. R.; Grunau, J.; Boden, S.; Steinhagen, J.; Martin, C.; Wimmer-Schweingruber, R. F.; Boettcher, S.; Seimetz, L.; Ravanbakhsh, A.; Elftmann, R.; Rodriguez-Pacheco, J.; Prieto, M.; Gomez-Herrero, R.

2013-12-01

The Energetic Particle Detector (EPD) suite for ESA's Solar Orbiter will provide key measurements to address particle acceleration at and near the Sun. The EPD suite consists of five sensors (STEP, SIS, EPT, and HET). The University of Kiel in Germany is also responsible for the design, development, and build of EPT and HET which are presented here. The Electron Proton Telescope (EPT) is designed to cleanly separate and measure electrons in the energy range from 20 - 400 keV and protons from 20 - 7000 keV. The Solar Orbiter EPT electron measurements from 20 - 400 keV will cover the gap with some overlap between suprathermal electrons measured by STEP and high energy electrons measured by HET. The proton measurements from 20 -7000 keV will partially cover the gap between STEP and HET. The Electron and Proton Telescope relies on the magnet/foil-technique. The High-Energy Telescope (HET) on ESA's Solar Orbiter mission, will measure electrons from 300 keV up to about 30 MeV, protons from 10 -100 MeV, and heavy ions from ~20 to 200 MeV/nuc. Thus, HET covers the energy range which is of specific interest for studies of the space environment and will perform the measurements needed to understand the origin of high-energy events at the Sun which occasionally accelerate particles to such high energies that they can penetrate the Earth's atmosphere and be measured at ground level. Here we present the current development status of EPT-HET units and calibration results of demonstration models and present plans for future activities.

Quantitative contribution of molecular orbitals to hydrogen bonding in a water dimer: Electron density projected integral (EDPI) analysis

NASA Astrophysics Data System (ADS)

Zhang, Zhiyuan; Jiang, Wanrun; Wang, Bo; Wang, Zhigang

2017-06-01

We introduce the orbital-resolved electron density projected integral (EDPI) along the H-bond in the real space to quantitatively investigate the specific contribution from the molecular orbitals (MOs) aspect in (H2O)2. Calculation results show that, the electronic occupied orbital (HOMO-4) of (H2O)2 accounts for about surprisingly 40% of the electron density at the bond critical point. Moreover, the electronic density difference analysis visualizes the electron accumulating effect of the orbital interaction within the H-bond between water molecules, supporting its covalent-like character. Our work expands the understanding of H-bond with specific contributions from certain MOs.

Mechanistic insights into energy conservation by flavin-based electron bifurcation.

PubMed

Lubner, Carolyn E; Jennings, David P; Mulder, David W; Schut, Gerrit J; Zadvornyy, Oleg A; Hoben, John P; Tokmina-Lukaszewska, Monika; Berry, Luke; Nguyen, Diep M; Lipscomb, Gina L; Bothner, Brian; Jones, Anne K; Miller, Anne-Frances; King, Paul W; Adams, Michael W W; Peters, John W

2017-06-01

The recently realized biochemical phenomenon of energy conservation through electron bifurcation provides biology with an elegant means to maximize utilization of metabolic energy. The mechanism of coordinated coupling of exergonic and endergonic oxidation-reduction reactions by a single enzyme complex has been elucidated through optical and paramagnetic spectroscopic studies revealing unprecedented features. Pairs of electrons are bifurcated over more than 1 volt of electrochemical potential by generating a low-potential, highly energetic, unstable flavin semiquinone and directing electron flow to an iron-sulfur cluster with a highly negative potential to overcome the barrier of the endergonic half reaction. The unprecedented range of thermodynamic driving force that is generated by flavin-based electron bifurcation accounts for unique chemical reactions that are catalyzed by these enzymes.

Energy Distribution of Electrons in Radiation Induced-Helium Plasmas. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Lo, R. H.

1972-01-01

Energy distribution of high energy electrons as they slow down and thermalize in a gaseous medium is studied. The energy distribution in the entire energy range from source energies down is studied analytically. A helium medium in which primary electrons are created by the passage of heavy-charged particles from nuclear reactions is emphasized. A radiation-induced plasma is of interest in a variety of applications, such as radiation pumped lasers and gaseous core nuclear reactors.

Calculated gadolinium atomic electron energy levels and Auger electron emission probability as a function of atomic number Z

NASA Astrophysics Data System (ADS)

Miloshevsky, G. V.; Tolkach, V. I.; Shani, Gad; Rozin, Semion

2002-06-01

Auger electron interaction with matter is gaining importance in particular in medical application of radiation. The production probability and energy spectrum is therefore of great importance. A good source of Auger electrons is the 157Gd(n,γ) 158Gd reaction. The present article describes calculations of electron levels in Gd atoms and provides missing data of outer electron energy levels. The energy of these electron levels missing in published tables, was found to be in the 23-24 and 6-7 eV energy ranges respectively. The probability of Auger emission was calculated as an interaction of wave function of the initial and final electron states. The wave functions were calculated using the Hartree-Fock-Slater approximation with relativistic correction. The equations were solved using a spherical symmetry potential. The error for inner shell level is less than 10%, it is increased to the order of 10-15% for the outer shells. The width of the Auger process changes from 0.1 to 1.2 eV for atomic number Z from 5 to 70. The fluorescence yield width changes five orders of magnitude in this range. Auger electron emission width from the K shell changes from 10 -2 to ˜1 eV with Z changing from 10 to 64, depending on the final state. For the L shell it changes from 0 to 0.25 when it Z changes from 20 to 64.

Destruction of Peptides and Nucleosides in Reactions with Low-Energy Electrons

NASA Astrophysics Data System (ADS)

Muftakhov, M. V.; Shchukin, P. V.

2018-05-01

Mass-spectrometry of negative ions is used to study dissociative electron capture by molecules of several nucleosides, simplest di- and tripeptides, and modified dipeptides. Energy domains and efficiencies of dissociative capture are determined for the objects under study, and threshold energies of several fragmentation processes are estimated. It is shown that cytidine and peptides are stable against fragmentation due to simple bond breaking at electron energies ranging from 0 to 1 eV.

``High energy Electron exPeriment (HEP)'' onboard the ERG satellite

NASA Astrophysics Data System (ADS)

Mitani, T.; Takashima, T.; Kasahara, S.; Miyake, W.; Hirahara, M.

2017-12-01

The Exploration of energization and Radiation in Geospace (ERG) satellite was successfully launched on December 20, 2016, and now explores how relativistic electrons in the radiation belts are generated during space storms. "High energy Electron exPeriment (HEP)" onboard the ERG satellite observes 70 keV - 2 MeV electrons and provides three-dimensional velocity distribution of electrons every spacecraft spin period. Electrons are observed by two types of camera designs, HEP-L and HEP-H, with regard to geometrical factor and energy range. HEP-L observes 0.1 - 1 MeV electrons and its geometrical factor (G-factor) is 10-3 cm2 str, and HEP-H observes 0.7 - 2 MeV and G-factor is 10-2 cm2 str. HEP-L and HEP-H each consist of three pin-hole type cameras, and each camera consist of mechanical collimator, stacked silicon semiconductor detectors and readout ASICs. HEP-H has larger opening angle of the collimator and more silicon detectors to observe higher energy electrons than HEP-L. The initial checkout in orbit was carried out in February 2017 and it was confirmed that there was no performance degradation by comparing the results of the initial checkout in orbit and the prelaunch function tests. Since late March, HEP has carried out normal observation. HEP observed losses and recovery of the outer radiation belt electrons several times up to now. In this presentation we introduce the HEP instrument design, prelaunch tests results and report the initial results in orbit.

Neutral beamline with ion energy recovery based on magnetic blocking of electrons

DOEpatents

Stirling, William L.

1982-01-01

A neutral beamline generator with energy recovery of the full-energy ion ponent of the beam based on magnetic blocking of electrons is provided. Ions from a positive ion source are accelerated to the desired beam energy from a slightly positive potential level with respect to ground through a neutralizer cell by means of a negative acceleration voltage. The unneutralized full-energy ion component of the beam exiting the neutralizer are retarded and slightly deflected and the electrons in the neutralizer are blocked by a magnetic field generated transverse to the beamline. An electron collector in the form of a coaxial cylinder surrounding and protruding axial a few centimeters beyond the neutralizer exit terminates the electrons which exit the neutralizer in an E x B drift to the collector when the collector is biased a few hundred volts positive with respect to the neutralizer voltage. The neutralizer is operated at the negative acceleration voltage, and the deflected full energy ions are decelerated and the charge collected at ground potential thereby expending none of their energy received from the acceleration power supply.

Observations of High Energy Cosmic Ray Electrons by the ATIC Balloon Experiment

NASA Technical Reports Server (NTRS)

Guzik, T. G.; Chang, J.; Adams, J. H., Jr.; Ahn, H. S.; Bashindzhagyan, G. L.; Christl, M.; Isbert, J.; Kim, K. C.; Kuznetsov, E. N.; Panasyuk, M. I.;

High energy primary electron spectrum observed by the emulsion chamber

NASA Technical Reports Server (NTRS)

Nishimura, J.; Fujii, M.; Aizu, H.; Hiraiwa, N.; Taira, T.; Kobayashi, T.; Niu, K.; Koss, T. A.; Lord, J. J.; Golden, R. L.

1978-01-01

A detector of the emulsion chamber type is used to measure the energy spectrum of cosmic-ray electrons. Two large emulsion chambers, each having an area of 40 by 50 sq cm, are exposed for about 25.5 hr at an average pressure altitude of 3.9 mbar. About 500 high-energy cascades (no less than about 600 GeV) are detected by searching for dark spots on the X-ray films. A power-law energy dependence formula is derived for the spectrum of primary cosmic-ray electrons in the energy region over 100 GeV. The results are in good agreement with the transition curves obtained previously by theoretical and Monte Carlo calculations.

Comparison of local exchange potentials of electron-N2 scattering

NASA Astrophysics Data System (ADS)

Rumble, J. R., Jr.; Truhlar, D. G.

1980-05-01

Vibrationally and electronically elastic electron scattering by N2 at 2-30 eV impact energy is considered. Static, static-exchange, and static-exchange-plus-polarization potentials, Cade-Sales-Wahl and INDO/1s wave functions, and semiclassical exchange and Hara free-electron-gas exchange potentials are examined. It is shown that the semiclassical exchange approximation is too attractive at low energy for N2. It is also shown quantitatively by consideration of partial and total integral cross sections how the effects of approximations to exchange become smaller as the incident energy is increased until the differences are about 8% for the total integral cross section at 30 eV.

Criticality of the electron-nucleus cusp condition to local effective potential-energy theories

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan Xiaoyin; Sahni, Viraht; Graduate School of the City University of New York, 360 Fifth Avenue, New York, New York 10016

2003-01-01

Local(multiplicative) effective potential energy-theories of electronic structure comprise the transformation of the Schroedinger equation for interacting Fermi systems to model noninteracting Fermi or Bose systems whereby the equivalent density and energy are obtained. By employing the integrated form of the Kato electron-nucleus cusp condition, we prove that the effective electron-interaction potential energy of these model fermions or bosons is finite at a nucleus. The proof is general and valid for arbitrary system whether it be atomic, molecular, or solid state, and for arbitrary state and symmetry. This then provides justification for all prior work in the literature based on themore » assumption of finiteness of this potential energy at a nucleus. We further demonstrate the criticality of the electron-nucleus cusp condition to such theories by an example of the hydrogen molecule. We show thereby that both model system effective electron-interaction potential energies, as determined from densities derived from accurate wave functions, will be singular at the nucleus unless the wave function satisfies the electron-nucleus cusp condition.« less

Characterization of radiation belt electron energy spectra from CRRES observations

NASA Astrophysics Data System (ADS)

Johnston, W. R.; Lindstrom, C. D.; Ginet, G. P.

2010-12-01

Energetic electrons in the outer radiation belt and the slot region exhibit a wide variety of energy spectral forms, more so than radiation belt protons. We characterize the spatial and temporal dependence of these forms using observations from the CRRES satellite Medium Electron Sensor A (MEA) and High-Energy Electron Fluxmeter (HEEF) instruments, together covering an energy range 0.15-8 MeV. Spectra were classified with two independent methods, data clustering and curve-fitting analyses, in each case defining categories represented by power law, exponential, and bump-on-tail (BOT) or other complex shapes. Both methods yielded similar results, with BOT, exponential, and power law spectra respectively dominating in the slot region, outer belt, and regions just beyond the outer belt. The transition from exponential to power law spectra occurs at higher L for lower magnetic latitude. The location of the transition from exponential to BOT spectra is highly correlated with the location of the plasmapause. In the slot region during the days following storm events, electron spectra were observed to evolve from exponential to BOT yielding differential flux minima at 350-650 keV and maxima at 1.5-2 MeV; such evolution has been attributed to energy-dependent losses from scattering by whistler hiss.

Theoretical and experimental differential cross sections for electron impact excitation of the electronic bands of furfural

NASA Astrophysics Data System (ADS)

Jones, D. B.; Neves, R. F. C.; Lopes, M. C. A.; da Costa, R. F.; do N. Varella, M. T.; Bettega, M. H. F.; Lima, M. A. P.; García, G.; Limão-Vieira, P.; Brunger, M. J.

2016-03-01

We report results from a joint experimental and theoretical investigation into electron scattering from the important industrial species furfural (C5H4O2). Specifically, differential cross sections (DCSs) have been measured and calculated for the electron-impact excitation of the electronic states of C5H4O2. The measurements were carried out at energies in the range 20-40 eV, and for scattered-electron angles between 10° and 90°. The energy resolution of those experiments was typically ˜80 meV. Corresponding Schwinger multichannel method with pseudo-potential calculations, for energies between 6-50 eV and with and without Born-closure, were also performed for a sub-set of the excited electronic-states that were accessed in the measurements. Those calculations were undertaken at the static exchange plus polarisation-level using a minimum orbital basis for single configuration interaction (MOB-SCI) approach. Agreement between the measured and calculated DCSs was qualitatively quite good, although to obtain quantitative accord, the theory would need to incorporate even more channels into the MOB-SCI. The role of multichannel coupling on the computed electronic-state DCSs is also explored in some detail.

Modelling relativistic effects in momentum-resolved electron energy loss spectroscopy of graphene

NASA Astrophysics Data System (ADS)

Lyon, K.; Mowbray, D. J.; Miskovic, Z. L.

2018-02-01

We present an analytical model for the electron energy loss through a two-dimensional (2D) layer of graphene, fully taking into account relativistic effects. Using two different models for graphene's 2D conductivity, one a two-fluid hydrodynamic model with an added correction to account for the inter-band electron transitions near the Dirac point in undoped graphene, the other derived from ab initio plane-wave time-dependent density functional theory in the frequency domain (PW-TDDFT-ω) calculations applied on a graphene superlattice, we derive various different expressions for the probability density of energy and momentum transfer from the incident electron to graphene. To further compare with electron energy loss spectroscopy (EELS) experiments that use setups like scanning Transmission Electron Microscopy, we integrated our energy loss functions over a range of wavenumbers, and compared how the choice of range directly affects the shape, position, and relative heights of graphene's π → π* and σ → σ* transition peaks. Comparisons were made with experimental EELS data under different model inputs, revealing again the strong effect that the choice of wavenumber range has on the energy loss.

Measurement of runaway electron energy distribution function during high-Z gas injection into runaway electron plateaus in DIII-D

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hollmann, E. M.; Moyer, R. A.; Rudakov, D. L.

2015-05-15

The evolution of the runaway electron (RE) energy distribution function f{sub ε} during massive gas injection into centered post-disruption runaway electron plateaus has been reconstructed. Overall, f{sub ε} is found to be much more skewed toward low energy than predicted by avalanche theory. The reconstructions also indicate that the RE pitch angle θ is not uniform, but tends to be large at low energies and small θ ∼ 0.1–0.2 at high energies. Overall power loss from the RE plateau appears to be dominated by collisions with background free and bound electrons, leading to line radiation. However, the drag on the plasma currentmore » appears to be dominated by collisions with impurity ions in most cases. Synchrotron emission appears not to be significant for overall RE energy dissipation but may be important for limiting the peak RE energy.« less

Measurement of runaway electron energy distribution function during high-Z gas injection into runaway electron plateaus in DIII-Da)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hollmann, E. M.; Parks, P. B.; Commaux, N.

2015-05-01

The evolution of the runaway electron (RE) energy distribution function fεfε during massive gas injection into centered post-disruption runaway electron plateaus has been reconstructed. Overall, fεfε is found to be much more skewed toward low energy than predicted by avalanche theory. The reconstructions also indicate that the RE pitch angle θ is not uniform, but tends to be large at low energies and small θ ~0.1–0.2 at high energies. Overall power loss from the RE plateau appears to be dominated by collisions with background free and bound electrons, leading to line radiation. However, the drag on the plasma current appearsmore » to be dominated by collisions with impurity ions in most cases. Synchrotron emission appears not to be significant for overall RE energy dissipation but may be important for limiting the peak RE energy.« less

Measurement of runaway electron energy distribution function during high-Z gas injection into runaway electron plateaus in DIII-D

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hollmann, E. M.; Parks, P. B.; Commaux, Nicolas J. C.

2015-05-14

The evolution of the runaway electron (RE) energy distribution function f ε during massive gas injection into centered post-disruption runaway electron plateaus has been reconstructed. Overall, f ε is found to be much more skewed toward low energy than predicted by avalanche theory. The reconstructions also indicate that the RE pitch angle theta is not uniform, but tends to be large at low energies and small theta similar to 0.1-0.2 at high energies. Overall power loss from the RE plateau appears to be dominated by collisions with background free and bound electrons, leading to line radiation. However, the drag onmore » the plasma current appears to be dominated by collisions with impurity ions in most cases. In conclusion, synchrotron emission appears not to be significant for overall RE energy dissipation but may be important for limiting the peak RE energy.« less

Electronic excitation of Na due to low-energy He collisions

NASA Astrophysics Data System (ADS)

Lin, C. Y.; Liebermann, H. P.

2005-05-01

In warm astrophysical environments electron collisions are the primary mechanism for thermalizing the internal energy of ambient atoms and molecules. However, in cool stellar and planetary atmospheres, the electron abundance is extremely low so that thermalization is only possible through collisions of the dominant neutral species, H2, He, and H. Typically, the neutral cross sections are much smaller than those due to electrons, so that the level populations of the atmospheric constituents may display departures from equilibrium. Unfortunately, these cross sections are generally not available for collision energies typical of stellar/planetary environments. In this work, we investigate the electronic excitation of Na due to collisions with He for energies near and just above threshold. The calculations are performed with the quantum-mechanical molecular-orbital close-coupling method utilizing ab initio adiabatic potential curves and nonadiabatic radial and rotational coupling matrix elements obtained from multireference single- and double- excitation configuration interaction approach. State-to-state cross sections and rate coefficients will be presented and compared with other theoretical and experimental data where available.

Low energy electron attachment to cyanamide (NH{sub 2}CN)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanzer, Katrin; Denifl, Stephan, E-mail: Andrzej.Pelc@poczta.umcs.lublin.pl, E-mail: Stephan.Denifl@uibk.ac.at; Pelc, Andrzej, E-mail: Andrzej.Pelc@poczta.umcs.lublin.pl, E-mail: Stephan.Denifl@uibk.ac.at

Cyanamide (NH{sub 2}CN) is a molecule relevant for interstellar chemistry and the chemical evolution of life. In the present investigation, dissociative electron attachment to NH{sub 2}CN has been studied in a crossed electron–molecular beams experiment in the electron energy range from about 0 eV to 14 eV. The following anionic species were detected: NHCN{sup −}, NCN{sup −}, CN{sup −}, NH{sub 2}{sup −}, NH{sup −}, and CH{sub 2}{sup −}. The anion formation proceeds within two broad electron energy regions, one between about 0.5 and 4.5 eV and a second between 4.5 and 12 eV. A discussion of possible reaction channels formore » all measured negative ions is provided. The experimental results are compared with calculations of the thermochemical thresholds of the anions observed. For the dehydrogenated parent anion, we explain the deviation between the experimental appearance energy of the anion with the calculated corresponding reaction threshold by electron attachment to the isomeric form of NH{sub 2}CN—carbodiimide.« less

MPGD2015: Low-energy electron source to characterize Micromegas/InGrid and study of dE/dx for low energy electrons

NASA Astrophysics Data System (ADS)

Attie, David; Barsuk, Sergey; Bezshyyko, Oleg; Burmistrov, Leonid; Chaus, Andrii; Colas, Paul; Fedorchuk, Oleksii; Golinka-Bezshyyko, Larisa; Haranko, Mykyta; Krylov, Vladyslav; Kubytskyi, Viacheslav; Lopez, Roberto; Monard, Hugues; Sukhonos, Daniil; Titov, Maxim; Tomassini, Davide; Variola, Alessandro; Rodin, Volodymyr

2018-02-01

Insert your english abstract here.A new versatile facility LEETECH for detector R&D, tests and calibration is designed and constructed. It uses electrons produced by the photoinjector PHIL at LAL, Orsay and provides a powerful tool for wide range R&D studies of different detector concepts delivering "monochromatic" samples of low energy electrons with adjustable energy and intensity. Among other innovative instrumentation techniques, LEETECH will be used for testing various gaseous tracking detectors and studying new Micromegas/InGrid concept which has very promising characteristics of spatial resolution and can be a good candidate for particle tracking and identification. In this paper the importance and expected characteristics of such facility based on detailed simulation studies are addressed.

Computation of energy states of hydrogenic quantum dot with two-electrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yakar, Y., E-mail: yuyakar@yahoo.com; Özmen, A., E-mail: aozmen@selcuk.edu.tr; Çakır, B., E-mail: bcakir@selcuk.edu.tr

2016-03-25

In this study we have investigated the electronic structure of the hydrogenic quantum dot with two electrons inside an impenetrable potential surface. The energy eigenvalues and wavefunctions of the ground and excited states of spherical quantum dot have been calculated by using the Quantum Genetic Algorithm (QGA) and Hartree-Fock Roothaan (HFR) method, and the energies are investigated as a function of dot radius. The results show that as dot radius increases, the energy of quantum dot decreases.

Ultralow energy calibration of LUX detector using Xe 127 electron capture

DOE PAGES

Akerib, D. S.; Alsum, S.; Araújo, H. M.; ...

2017-12-01

We report an absolute calibration of the ionization yields(more » $$\\textit{Q$$_y$})$ and fluctuations for electronic recoil events in liquid xenon at discrete energies between 186 eV and 33.2 keV. The average electric field applied across the liquid xenon target is 180 V/cm. The data are obtained using low energy $$^{127}$$Xe electron capture decay events from the 95.0-day first run from LUX (WS2013) in search of Weakly Interacting Massive Particles (WIMPs). The sequence of gamma-ray and X-ray cascades associated with $$^{127}$$I de-excitations produces clearly identified 2-vertex events in the LUX detector. We observe the K- (binding energy, 33.2 keV), L- (5.2 keV), M- (1.1 keV), and N- (186 eV) shell cascade events and verify that the relative ratio of observed events for each shell agrees with calculations. The N-shell cascade analysis includes single extracted electron (SE) events and represents the lowest-energy electronic recoil $$\\textit{in situ}$$ measurements that have been explored in liquid xenon.« less

Ultralow energy calibration of LUX detector using Xe 127 electron capture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akerib, D. S.; Alsum, S.; Araújo, H. M.

We report an absolute calibration of the ionization yields (Q y) and fluctuations for electronic recoil events in liquid xenon at discrete energies between 186 eV and 33.2 keV. The average electric field applied across the liquid xenon target is 180 V/cm. The data are obtained using low energy 127Xe electron capture decay events from the 95.0-day first run from LUX (WS2013) in search of weakly interacting massive particles. The sequence of gamma-ray and x-ray cascades associated with 127I deexcitations produces clearly identified two-vertex events in the LUX detector. We observe the K-(binding energy, 33.2 keV), L-(5.2 keV), M-(1.1 keV),more » and N-(186 eV) shell cascade events and verify that the relative ratio of observed events for each shell agrees with calculations. In conclusion, the N-shell cascade analysis includes single extracted electron (SE) events and represents the lowest-energy electronic recoil in situ measurements that have been explored in liquid xenon.« less

Ultralow energy calibration of LUX detector using Xe 127 electron capture

DOE PAGES

Akerib, D. S.; Alsum, S.; Araújo, H. M.; ...

2017-12-28

We report an absolute calibration of the ionization yields (Q y) and fluctuations for electronic recoil events in liquid xenon at discrete energies between 186 eV and 33.2 keV. The average electric field applied across the liquid xenon target is 180 V/cm. The data are obtained using low energy 127Xe electron capture decay events from the 95.0-day first run from LUX (WS2013) in search of weakly interacting massive particles. The sequence of gamma-ray and x-ray cascades associated with 127I deexcitations produces clearly identified two-vertex events in the LUX detector. We observe the K-(binding energy, 33.2 keV), L-(5.2 keV), M-(1.1 keV),more » and N-(186 eV) shell cascade events and verify that the relative ratio of observed events for each shell agrees with calculations. In conclusion, the N-shell cascade analysis includes single extracted electron (SE) events and represents the lowest-energy electronic recoil in situ measurements that have been explored in liquid xenon.« less

Diffraction of electrons at intermediate energies: The role of phonons

NASA Astrophysics Data System (ADS)

Ascolani, H.; Zampieri, G.

1996-07-01

The intensity of electrons reflected ``elastically'' from crystalline surfaces presents two regimes: the low-energy or LEED regime (<500 eV), in which the electrons are reflected along the Bragg directions, and the intermediate-energy or XPD/AED regime (>500 eV), in which the maxima of intensity are along the main crystallographic axes. We present a model which explains this transition in terms of the excitation/absorption of phonons during the scattering.

Energy principle for excitations in plasmas with counterstreaming electron flows

NASA Astrophysics Data System (ADS)

Kumar, Atul; Shukla, Chandrasekhar; Das, Amita; Kaw, Predhiman

2018-05-01

A relativistic electron beam propagating through plasma induces a return electron current in the system. Such a system of interpenetrating forward and return electron current is susceptible to a host of instabilities. The physics of such instabilities underlies the conversion of the flow kinetic energy to the electromagnetic field energy. Keeping this in view, an energy principle analysis has been enunciated in this paper. Such analyses have been widely utilized earlier in the context of conducting fluids described by MHD model [I. B. Bernstein et al., Proceedings of the Royal Society of London A: Mathematical, Physical and Engineering Sciences 244(1236), 17-40 (1958)]. Lately, such an approach has been employed for the electrostatic two stream instability for the electron beam plasma system [C. N. Lashmore-Davies, Physics of Plasmas 14(9), 092101 (2007)]. In contrast, it has been shown here that even purely growing mode like Weibel/current filamentation instability for the electron beam plasma system is amenable to such a treatment. The treatment provides an understanding of the energetics associated with the growing mode. The growth rate expression has also been obtained from it. Furthermore, it has been conclusively demonstrated in this paper that for identical values of S4=∑αn0 αv0α 2/n0γ0 α, the growth rate is higher when the counterstreaming beams are symmetric (i.e. S3 = ∑αn0αv 0α/n0γ0α = 0) compared to the case when the two beams are asymmetric (i.e. when S3 is finite). Here, v 0α, n0α and γ0α are the equilibrium velocity, electron density and the relativistic factor for the electron species `α' respectively and n0 = ∑αn0α is the total electron density. Particle - In - Cell simulations have been employed to show that the saturated amplitude of the field energy is also higher in the symmetric case.

Mechanistic insights into energy conservation by flavin-based electron bifurcation

DOE PAGES

Lubner, Carolyn E.; Jennings, David P.; Mulder, David W.; ...

2017-04-10

The recently realized biochemical phenomenon of energy conservation through electron bifurcation provides biology with an elegant means to maximize utilization of metabolic energy. The mechanism of coordinated coupling of exergonic and endergonic oxidation-reduction reactions by a single enzyme complex has been elucidated through optical and paramagnetic spectroscopic studies revealing unprecedented features. Pairs of electrons are bifurcated over more than 1 volt of electrochemical potential by generating a low-potential, highly energetic, unstable flavin semiquinone and directing electron flow to an iron-sulfur cluster with a highly negative potential to overcome the barrier of the endergonic half reaction. As a result, the unprecedentedmore » range of thermodynamic driving force that is generated by flavin-based electron bifurcation accounts for unique chemical reactions that are catalyzed by these enzymes.« less

Mechanistic insights into energy conservation by flavin-based electron bifurcation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lubner, Carolyn E.; Jennings, David P.; Mulder, David W.

The recently realized biochemical phenomenon of energy conservation through electron bifurcation provides biology with an elegant means to maximize utilization of metabolic energy. The mechanism of coordinated coupling of exergonic and endergonic oxidation-reduction reactions by a single enzyme complex has been elucidated through optical and paramagnetic spectroscopic studies revealing unprecedented features. Pairs of electrons are bifurcated over more than 1 volt of electrochemical potential by generating a low-potential, highly energetic, unstable flavin semiquinone and directing electron flow to an iron-sulfur cluster with a highly negative potential to overcome the barrier of the endergonic half reaction. As a result, the unprecedentedmore » range of thermodynamic driving force that is generated by flavin-based electron bifurcation accounts for unique chemical reactions that are catalyzed by these enzymes.« less

s-wave threshold in electron attachment - Results in 2-C4F6 and CFCl3 at ultra-low electron energies

NASA Technical Reports Server (NTRS)

Chutjian, A.; Alajajian, S. H.; Ajello, J. M.; Orient, O. J.

1984-01-01

Electron attachment lineshapes and cross sections are reported for the processes 2-C4F6(-)/2-C4F6 and Cl(-)/CFCl3 at electron energies of 0-120 and 0-140 meV, and at resolutions of 6 and 7 meV (FWHM), respectively. As in previous measurements in CCl4 and SF6, the results show resolution-limited narrow structure in the cross section at electron energies below 15 meV. This structure arises from the divergence of the s-wave cross section in the limit of zero electron energy. Comparisons are given with swarm-measured results, and with collisional ionization (high-Rydberg attachment) data in this energy range.

Advanced High Energy Density Secondary Batteries with Multi‐Electron Reaction Materials

PubMed Central

Luo, Rui; Huang, Yongxin; Li, Li

2016-01-01

Secondary batteries have become important for smart grid and electric vehicle applications, and massive effort has been dedicated to optimizing the current generation and improving their energy density. Multi‐electron chemistry has paved a new path for the breaking of the barriers that exist in traditional battery research and applications, and provided new ideas for developing new battery systems that meet energy density requirements. An in‐depth understanding of multi‐electron chemistries in terms of the charge transfer mechanisms occuring during their electrochemical processes is necessary and urgent for the modification of secondary battery materials and development of secondary battery systems. In this Review, multi‐electron chemistry for high energy density electrode materials and the corresponding secondary battery systems are discussed. Specifically, four battery systems based on multi‐electron reactions are classified in this review: lithium‐ and sodium‐ion batteries based on monovalent cations; rechargeable batteries based on the insertion of polyvalent cations beyond those of alkali metals; metal–air batteries, and Li–S batteries. It is noted that challenges still exist in the development of multi‐electron chemistries that must be overcome to meet the energy density requirements of different battery systems, and much effort has more effort to be devoted to this. PMID:27840796

New High Energy Electron Component of Earth Radiation Belt

NASA Astrophysics Data System (ADS)

Dmitrenko, V. V.; Galper, A. M.; Gratchev, V. M.; Kirillov-Ugryumov, V. G.; Ulin, S. E.; Voronov, S. A.

The Earth Radiation Belt (ERB) was discovered in the course of the first flights of Russian and American satellites with conventional instruments (gas discharge and scintillation counters), which made it possible to investigate many characteristics of trapped particles and simulate adequate radiation belt models. However, the experimental and theoretical evidence accumulated over recent time, needs more elaborate measurements for its interpretation. These measurements became feasible after the development of devices based on more perfect detectors (solid and gas-filled Cherenkov detectors, magnetic spectrometer, scintillation time-of-flight systems). The evidence requiring new direct measurements in the ERB was obtained in the late 1960s in the course of balloon flights carried out by Cosmophysics Laboratory of the Moscow Engineering and Physics Institute. In these flights a correlation between the high energy electron flux in the upper atmosphere and perturbations ofthe Earth's magnetosphere was established. This phenomenon could be explained assuming there exist high energy electron fluxes in the ERB. High energy electron fluxes in the ERB were recorded for the first time in the direct experiments carried out on board orbital station 'Salyut-6' (orbit altitude - 350 km, inclination 51.6 deg). A scintillation-Cherenkov telescope 'Elena' controlled by cosmonauts was preset to different programmed positions. The measurements were made in the periphery of the ERB, namely, in the part which goes as low as several hundred km in the Brazil Anomaly Region (BRA). The flux of electrons with energies above 30 MeV was up to 104 (m2s sr)-1.

Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope.

PubMed

Govyadinov, Alexander A; Konečná, Andrea; Chuvilin, Andrey; Vélez, Saül; Dolado, Irene; Nikitin, Alexey Y; Lopatin, Sergei; Casanova, Fèlix; Hueso, Luis E; Aizpurua, Javier; Hillenbrand, Rainer

2017-07-21

Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.Here the authors adapt a STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in hexagonal boron nitride, revealing that the electron loss is dominated by hyperbolic phonon polaritons.

High energy electron acceleration with PW-class laser system

NASA Astrophysics Data System (ADS)

Nakanii, N.; Kondo, K.; Mori, Y.; Miura, E.; Yabuuchi, T.; Tsuji, K.; Suzuki, S.; Asaka, T.; Yanagida, K.; Hanaki, H.; Kobayashi, T.; Makino, K.; Yamane, T.; Miyamoto, S.; Horikawa, K.; Kimura, K.; Takeda, K.; Fukumochi, S.; Kashihara, M.; Tanimoto, T.; Nakamura, H.; Ishikura, T.; Tampo, M.; Kodama, R.; Kitagawa, Y.; Mima, K.; Tanaka, K. A.

2008-06-01

We performed electron acceleration experiment with PW-class laser and a plasma tube, which was created by imploding a hollow polystyrene cylinder. In this experiment, electron energies in excess of 600 MeV have been observed. Moreover, the spectra of a comparatively high-density plasma ˜1019 cm-3 had a bump around 10 MeV. Additionally, we performed the absolute sensitivity calibration of imaging plate for 1 GeV electrons from the injector Linac of Spring-8 in order to evaluate absolute number of GeV-class electrons in the laser acceleration experiment.

Quantitative trait loci analysis for net ginning energy requirements in upland cotton (Gossypium hirsutum L.)

USDA-ARS?s Scientific Manuscript database

Cotton cultivars with reduced fiber-seed attachment force have the potential to be ginned faster with less energy. The objective of this study was to identify quantitative trait loci (QTL) for net ginning energy (NGE) requirement, and its relationship with other fiber quality traits in upland cotton...

Considerable knock-on displacement of metal atoms under a low energy electron beam.

PubMed

Gu, Hengfei; Li, Geping; Liu, Chengze; Yuan, Fusen; Han, Fuzhou; Zhang, Lifeng; Wu, Songquan

2017-03-15

Under electron beam irradiation, knock-on atomic displacement is commonly thought to occur only when the incident electron energy is above the incident-energy threshold of the material in question. However, we report that when exposed to intense electrons at room temperature at a low incident energy of 30 keV, which is far below the theoretically predicted incident-energy threshold of zirconium, Zircaloy-4 (Zr-1.50Sn-0.25Fe-0.15Cr (wt.%)) surfaces can undergo considerable displacement damage. We demonstrate that electron beam irradiation of the bulk Zircaloy-4 surface resulted in a striking radiation effect that nanoscale precipitates within the surface layer gradually emerged and became clearly visible with increasing the irradiation time. Our transmission electron microscope (TEM) observations further reveal that electron beam irradiation of the thin-film Zircaly-4 surface caused the sputtering of surface α-Zr atoms, the nanoscale atomic restructuring in the α-Zr matrix, and the amorphization of precipitates. These results are the first direct evidences suggesting that displacement of metal atoms can be induced by a low incident electron energy below threshold. The presented way to irradiate may be extended to other materials aiming at producing appealing properties for applications in fields of nanotechnology, surface technology, and others.

Vertical detachment energy of hydrated electron based on a modified form of solvent reorganization energy.

PubMed

Wang, Xing-Jian; Zhu, Quan; Li, Yun-Kui; Cheng, Xue-Min; Li, Xiang-Yuan; Fu, Ke-Xiang; He, Fu-Cheng

2010-02-18

In this work, the constrained equilibrium principle is introduced and applied to the derivations of the nonequilibrium solvation free energy and solvent reorganization energy in the process of removing the hydrated electron. Within the framework of the continuum model, a modified expression of the vertical detachment energy (VDE) of a hydrated electron in water is formulated. Making use of the approximation of spherical cavity and point charge, the variation tendency of VDE accompanying the size increase of the water cluster has been inspected. Discussions comparing the present form of the VDE and the traditional one and the influence of the cavity radius in either the fixed pattern or the varying pattern on the VDE have been made.

Electronic transport coefficients in plasmas using an effective energy-dependent electron-ion collision-frequency

NASA Astrophysics Data System (ADS)

Faussurier, G.; Blancard, C.; Combis, P.; Decoster, A.; Videau, L.

2017-10-01

We present a model to calculate the electrical and thermal electronic conductivities in plasmas using the Chester-Thellung-Kubo-Greenwood approach coupled with the Kramers approximation. The divergence in photon energy at low values is eliminated using a regularization scheme with an effective energy-dependent electron-ion collision-frequency. Doing so, we interpolate smoothly between the Drude-like and the Spitzer-like regularizations. The model still satisfies the well-known sum rule over the electrical conductivity. Such kind of approximation is also naturally extended to the average-atom model. A particular attention is paid to the Lorenz number. Its nondegenerate and degenerate limits are given and the transition towards the Drude-like limit is proved in the Kramers approximation.

Inspection applications with higher electron beam energies

NASA Astrophysics Data System (ADS)

Norman, D. R.; Jones, J. L.; Yoon, W. Y.; Haskell, K. J.; Sterbentz, J. W.; Zabriskie, J. M.; Hunt, A. W.; Harmon, F.; Kinlaw, M. T.

2005-12-01

The Idaho National Laboratory has developed prototype shielded nuclear material detection systems based on pulsed photonuclear assessment (PPA) techniques for the inspection of cargo containers. During this work, increased nuclear material detection capabilities have been demonstrated at higher electron beam energies than those allowed by federal regulations for cargo inspection. This paper gives a general overview of a nuclear material detection system, the PPA technique and discusses the benefits of using these higher energies. This paper also includes a summary of the numerical and test results from LINAC operations up to 24 MeV and discusses some of the federal energy limitations associated with cargo inspection.

Role of bremsstrahlung radiation in limiting the energy of runaway electrons in tokamaks.

PubMed

Bakhtiari, M; Kramer, G J; Takechi, M; Tamai, H; Miura, Y; Kusama, Y; Kamada, Y

2005-06-03

Bremsstrahlung radiation of runaway electrons is found to be an energy limit for runaway electrons in tokamaks. The minimum and maximum energy of runaway electron beams is shown to be limited by collisions and bremsstrahlung radiation, respectively. It is also found that a massive injection of a high-Z gas such as xenon can terminate a disruption-generated runaway current before the runaway electrons hit the walls.

Electron scattering measurements from molecules of technological relevance

NASA Astrophysics Data System (ADS)

Jones, Darryl

2014-10-01

Biomass represents a significant opportunity to provide renewable and sustainable biofuels. Non-thermal atmospheric pressure plasmas provide an opportunity to efficiently breakdown the naturally-resilient biomass into its useful subunits. Free electrons produced in the plasma may assist in this process by inducing fragmentation though dissociative excitation, ionization or attachment processes. To assist in understanding and refining this process, we have performed electron energy loss experiments from phenol (C6H5OH), a key structural building block of biomass. This enables a quantitative assessment of the excited electronic states of phenol. Differential cross sections for the electron-driven excitation of phenol have also been obtained for incident electron energies in the 20--250 eV range and over 3--90° scattering angles. DBJ acknowledges financial support provided by an Australian Research Council DECRA.

a Study of the Tungsten (001) Surface Using Low Energy Electron Diffraction and Other Electron Spectroscopies.

NASA Astrophysics Data System (ADS)

Kalceff, Marion Anne Stevens

The properties of the clean Tungsten (001) surfaces (both (1 x 1) and reconstructed (SQRT.(2 x SQRT.(2)R45(DEGREES) phases) and the effects of the common absorbates Hydrogen and Oxygen have been investigated using the techniques of Low Energy Electron Diffraction, Auger Electron Spectroscopy and Characteristic Electron Energy Loss Spectroscopy. The origins of features observed in Characteristic Energy Loss Spectra, very low energy (<10 eV) Secondary Electron Emission spectra and low energy (<40 eV) Auger spectra, are deduced and compared with recent relevant independently obtained theoretical data and with other, sometimes conflicting, analyses. The use of these spectroscopies as monitors of surface cleanliness is evaluated. In particular a previously unreported emission, observed during Oxygen adsorption, is attributed to an Auger transition involving the Oxygen 2s and 2p adsorbate levels. Experimental conventional LEED and improved resolution very low energy intensity versus energy spectra are compared with Dynamical spectra, calculated using the program package of M. A. Van Hove and S. Y. Tong or calculated by R. O. Jones using a previously determined saturated image barrier, within a spin dependent scattering model, respectively. Structural information about the clean (1 x 1), clean reconstructed (SQRT.(2 x SQRT.(2)R45(DEGREES) and Hydrogen saturated (1 x 1)-H surfaces have been obtained via visual comparison or R factor (E. Zanazzi and F. Jona) analysis of the conventional data. The conventional methods of LEED Intensity data collection are assessed and procedures to improve experimental reproducibility are proposed. From the analysis of the improved resolution data, and with reference to the corresponding set of very low energy electron reflection data also obtained for comparison, conclusions are made about the origins of fine structure observed in the experimental profiles and about the W(001) surface order before and after the temperature dependent

Additive effects of electronic and nuclear energy losses in irradiation-induced amorphization of zircon

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 reducedmore » damage, while the electronic electron-phonon interactions have additive impact on the final damage created per ion.« less

Low-energy electron collisions with biomolecules

NASA Astrophysics Data System (ADS)

Winstead, Carl; McKoy, Vincent

2012-11-01

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

The DarkSide-50 Experiment: Electron Recoil Calibrations and A Global Energy Variable

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hackett, Brianne Rae

2017-01-01

Over the course of decades, there has been mounting astronomical evidence for non-baryonic dark matter, yet its precise nature remains elusive. A favored candidate for dark matter is the Weakly Interacting Massive Particle (WIMP) which arises naturally out of extensions to the Standard Model. WIMPs are expected to occasionally interact with particles of normal matter through nuclear recoils. DarkSide-50 aims to detect this type of particle through the use of a two-phase liquid argon time projection chamber. To make a claim of discovery, an accurate understanding of the background and WIMP search region is imperative. Knowledge of the backgrounds ismore » done through extensive studies of DarkSide-50's response to electron and nuclear recoils. The CALibration Insertion System (CALIS) was designed and built for the purpose of introduc- ing radioactive sources into or near the detector in a joint eort between Fermi National Laboratory (FNAL) and the University of Hawai'i at Manoa. This work describes the testing, installation, and commissioning of CALIS at the Laboratori Nazionali del Gran Sasso. CALIS has been used in mul- tiple calibration campaigns with both neutron and sources. In this work, DarkSide-50's response to electron recoils, which are important for background estimations, was studied through the use of calibration sources by constructing a global energy variable which takes into account the anti- correlation between scintillation and ionization signals produced by interactions in the liquid argon. Accurately reconstructing the event energy correlates directly with quantitatively understanding the WIMP sensitivity in DarkSide-50. This work also validates the theoretically predicted decay spectrum of 39Ar against 39Ar decay data collected in the early days of DarkSide-50 while it was lled with atmospheric argon; a validation of this type is not readily found in the literature. Finally, we show how well the constructed energy variable can predict energy

Resolving runaway electron distributions in space, time, and energy

NASA Astrophysics Data System (ADS)

Paz-Soldan, C.; Cooper, C. M.; Aleynikov, P.; Eidietis, N. W.; Lvovskiy, A.; Pace, D. C.; Brennan, D. P.; Hollmann, E. M.; Liu, C.; Moyer, R. A.; Shiraki, D.

2018-05-01

Areas of agreement and disagreement with present-day models of runaway electron (RE) evolution are revealed by measuring MeV-level bremsstrahlung radiation from runaway electrons (REs) with a pinhole camera. Spatially resolved measurements localize the RE beam, reveal energy-dependent RE transport, and can be used to perform full two-dimensional (energy and pitch-angle) inversions of the RE phase-space distribution. Energy-resolved measurements find qualitative agreement with modeling on the role of collisional and synchrotron damping in modifying the RE distribution shape. Measurements are consistent with predictions of phase-space attractors that accumulate REs, with non-monotonic features observed in the distribution. Temporally resolved measurements find qualitative agreement with modeling on the impact of collisional and synchrotron damping in varying the RE growth and decay rate. Anomalous RE loss is observed and found to be largest at low energy. Possible roles for kinetic instability or spatial transport to resolve these anomalies are discussed.

Energy modulation of nonrelativistic electrons in an optical near field on a metal microslit

NASA Astrophysics Data System (ADS)

Ishikawa, R.; Bae, J.; Mizuno, K.

2001-04-01

Energy modulation of nonrelativistic electrons with a laser beam using a metal microslit as an interaction circuit has been investigated. An optical near field is induced in the proximity of the microslit by illumination of the laser beam. The electrons passing close to the slit are accelerated or decelerated by an evanescent wave contained in the near field whose phase velocity is equal to the velocity of the electrons. The electron-evanescent wave interaction in the microslit has been analyzed theoretically and experimentally. The theory has predicted that electron energy can be modulated at optical frequencies. Experiments performed in the infrared region have verified theoretical predictions. The electron-energy changes of more than ±5 eV with a 10 kW CO2 laser pulse at the wavelength of 10.6 μm has been successfully observed for an electron beam with an energy of less than 80 keV.

Low-energy Spectra of Gamma-Ray Bursts from Cooling Electrons

NASA Astrophysics Data System (ADS)

Geng, Jin-Jun; Huang, Yong-Feng; Wu, Xue-Feng; Zhang, Bing; Zong, Hong-Shi

2018-01-01

The low-energy spectra of gamma-ray bursts’ (GRBs) prompt emission are closely related to the energy distribution of electrons, which is further regulated by their cooling processes. We develop a numerical code to calculate the evolution of the electron distribution with given initial parameters, in which three cooling processes (i.e., adiabatic, synchrotron, and inverse Compton cooling) and the effect of a decaying magnetic field are coherently considered. A sequence of results is presented by exploring the plausible parameter space for both the fireball and the Poynting flux–dominated regime. Different cooling patterns for the electrons can be identified, and they are featured by a specific dominant cooling mechanism. Our results show that the hardening of the low-energy spectra can be attributed to the dominance of synchrotron self-Compton cooling within the internal shock model or to decaying synchrotron cooling within the Poynting flux–dominated jet scenario. These two mechanisms can be distinguished by observing the hard low-energy spectra of isolated short pulses in some GRBs. The dominance of adiabatic cooling can also lead to hard low-energy spectra when the ejecta is moving at an extreme relativistic speed. The information from the time-resolved low-energy spectra can help to probe the physical characteristics of the GRB ejecta via our numerical results.

Some effects of electron channeling on electron energy loss spectroscopy.

PubMed

Kirkland, Earl J

2005-02-01

As an electron beam (of order 100 keV) travels through a crystalline solid it can be channeled down a zone axis of the crystal to form a channeling peak centered on the atomic columns. The channeling peak can be similar in size to the outer atomic orbitals. Electron energy loss spectroscopy (EELS) measures the losses that the electron experiences as it passes through the solid yielding information about the unoccupied density of states in the solid. The interaction matrix element for this process typically produces dipole selection rules for small angle scattering. In this paper, a theoretical calculation of the EELS cross section in the presence of strong channeling is performed for the silicon L23 edge. The presence of channeling is found to alter both the intensity and selection rules for this EELS signal as a function of depth in the solid. At some depths in the specimen small but significant non-dipole transition components can be produced, which may influence measurements of the density of states in solids.

Low-energy electron-phonon effective action from symmetry analysis

NASA Astrophysics Data System (ADS)

Cabra, D. C.; Grandi, N. E.; Silva, G. A.; Sturla, M. B.

2013-07-01

Based on a detailed symmetry analysis, we state the general rules to build up the effective low-energy field theory describing a system of electrons weakly interacting with the lattice degrees of freedom. The basic elements in our construction are what we call the “memory tensors,” which keep track of the microscopic discrete symmetries into the coarse-grained action. The present approach can be applied to lattice systems in arbitrary dimensions and in a systematic way to any desired order in derivatives. We apply the method to the honeycomb lattice and reobtain the by-now well-known effective action of Dirac fermions coupled to fictitious gauge fields. As a second example, we derive the effective action for electrons in the kagome lattice, where our approach allows us to obtain in a simple way the low-energy electron-phonon coupling terms.

A quantitative structure–function relationship for the Photosystem II reaction center: Supermolecular behavior in natural photosynthesis

PubMed Central

Barter, Laura M. C.; Durrant, James R.; Klug, David R.

2003-01-01

Light-induced charge separation is the primary photochemical event of photosynthesis. Efficient charge separation in photosynthetic reaction centers requires the balancing of electron and excitation energy transfer processes, and in Photosystem II (PSII), these processes are particularly closely entangled. Calculations that treat the cofactors of the PSII reaction center as a supermolecular complex allow energy and electron transfer reactions to be described in a unified way. This calculational approach is shown to be in good agreement with experimentally observed energy and electron transfer dynamics. This supermolecular view also correctly predicts the effect of changing the redox potentials of cofactors by site-directed mutagenesis, thus providing a unified and quantitative structure–function relationship for the PSII reaction center. PMID:12538865

New electron-energy transfer rates for vibrational excitation of O2

NASA Astrophysics Data System (ADS)

Jones, D. B.; Campbell, L.; Bottema, M. J.; Brunger, M. J.

2003-09-01

We report on our computation of electron-energy transfer rates for vibrational excitation of O2. This work was necessitated by inadequacies in the electron-impact cross section databases employed in previous studies and, in one case, an inaccurate approximate formulation to the rate equation. Both these inadequacies led to incorrect energy transfer rates being published in the literature. We also demonstrate the importance of using cross sections that encompass an energy range that is extended enough to appropriately describe the environment under investigation.

Electron dynamics in high energy density plasma bunch generation driven by intense picosecond laser pulse

NASA Astrophysics Data System (ADS)

Li, M.; Yuan, T.; Xu, Y. X.; Luo, S. N.

2018-05-01

When an intense picosecond laser pulse is loaded upon a dense plasma, a high energy density plasma bunch, including electron bunch and ion bunch, can be generated in the target. We simulate this process through one-dimensional particle-in-cell simulation and find that the electron bunch generation is mainly due to a local high energy density electron sphere originated in the plasma skin layer. Once generated the sphere rapidly expands to compress the surrounding electrons and induce high density electron layer, coupled with that, hot electrons are efficiently triggered in the local sphere and traveling in the whole target. Under the compressions of light pressure, forward-running and backward-running hot electrons, a high energy density electron bunch generates. The bunch energy density is as high as TJ/m3 order of magnitude in our conditions, which is significant in laser driven dynamic high pressure generation and may find applications in high energy density physics.

Low-energy Auger electron diffraction: influence of multiple scattering and angular momentum

NASA Astrophysics Data System (ADS)

Chassé, A.; Niebergall, L.; Kucherenko, Yu.

2002-04-01

The angular dependence of Auger electrons excited from single-crystal surfaces is treated theoretically within a multiple-scattering cluster model taking into account the full Auger transition matrix elements. In particular the model has been used to discuss the influence of multiple scattering and angular momentum of the Auger electron wave on Auger electron diffraction (AED) patterns in the region of low kinetic energies. Theoretical results of AED patterns are shown and discussed in detail for Cu(0 0 1) and Ni(0 0 1) surfaces, respectively. Even though Cu and Ni are very similar in their electronic and scattering properties recently strong differences have been found in AED patterns measured in the low-energy region. It is shown that the differences may be caused to superposition of different electron diffraction effects in an energy-integrated experiment. A good agreement between available experimental and theoretical results has been achieved.

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.

Opto-electronic conversion logic behaviour through dynamic modulation of electron/energy transfer states at the TiO2-carbon quantum dot interface.

PubMed

Wang, Fang; Zhang, Yonglai; Liu, Yang; Wang, Xuefeng; Shen, Mingrong; Lee, Shuit-Tong; Kang, Zhenhui

2013-03-07

Here we show a bias-mediated electron/energy transfer process at the CQDs-TiO(2) interface for the dynamic modulation of opto-electronic properties. Different energy and electron transfer states have been observed in the CQDs-TNTs system due to the up-conversion photoluminescence and the electron donation/acceptance properties of the CQDs decorated on TNTs.

Note: Electron energy spectroscopy mapping of surface with scanning tunneling microscope.

PubMed

Li, Meng; Xu, Chunkai; Zhang, Panke; Li, Zhean; Chen, Xiangjun

2016-08-01

We report a novel scanning probe electron energy spectrometer (SPEES) which combines a double toroidal analyzer with a scanning tunneling microscope to achieve both topography imaging and electron energy spectroscopy mapping of surface in situ. The spatial resolution of spectroscopy mapping is determined to be better than 0.7 ± 0.2 μm at a tip sample distance of 7 μm. Meanwhile, the size of the field emission electron beam spot on the surface is also measured, and is about 3.6 ± 0.8 μm in diameter. This unambiguously demonstrates that the spatial resolution of SPEES technique can be much better than the size of the incident electron beam.

Note: Electron energy spectroscopy mapping of surface with scanning tunneling microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Meng; Xu, Chunkai, E-mail: xuck@ustc.edu.cn, E-mail: xjun@ustc.edu.cn; Zhang, Panke

We report a novel scanning probe electron energy spectrometer (SPEES) which combines a double toroidal analyzer with a scanning tunneling microscope to achieve both topography imaging and electron energy spectroscopy mapping of surface in situ. The spatial resolution of spectroscopy mapping is determined to be better than 0.7 ± 0.2 μm at a tip sample distance of 7 μm. Meanwhile, the size of the field emission electron beam spot on the surface is also measured, and is about 3.6 ± 0.8 μm in diameter. This unambiguously demonstrates that the spatial resolution of SPEES technique can be much better than themore » size of the incident electron beam.« less

Development of a low energy electron spectrometer for SCOPE

NASA Astrophysics Data System (ADS)

Tominaga, Y.; Saito, Y.; Yokota, S.

2010-12-01

We are newly developing an electrostatic analyzer which measures low energy electrons for the future satellite mission SCOPE (cross Scale COupling in the Plasma universE). The main purpose of the SCOPE mission is to understand the cross scale coupling between macroscopic MHD scale phenom- ena and microscopic ion and electron scale phenomena. In order to understand the dynamics of plasma in such small scales, we need to observe the plasma with an analyzer which has high time resolutions. In the Earth's magnetosphere, typical timescale of plasma cyclotron frequency is ~10 sec (ions) and ~ 10 msec (electrons). In order to conduct electron-scale observations, an analyzer which has a very high time resolution(~ 10 msec) is necessary for the experiment. So far, we decided a design of the analyzer. The analyzer has three nested spherical/toroidal deflectors, which enables us to measure two different energies simultaneously and shorten the time resolution of the experiment. In order to obtain 3D velocity distribution functions of electrons, the analyzer must have 4-pi steradian field of view. We will install 8 sets of the analyzers on the satellite. Using all these analyzers we will secure 4-pi str fov at the same time. In the experiment, we plan to measure electrons from 10 eV to 22.5 keV with 32 steps. Given that the sampling time of the experiment is 0.5 msec, it takes about 8 msec to measure the whole energy range, then the time resolution of the experiment is 8 msec. The energy and angular resolution of the inner analyzer is 0.23 and 16 degrees, respectively, and that of the outer analyzer is 0.17 and 11.5 degrees, respectively. To measure enough electrons within the sampling time, the analyzer is designed to have geometrical factors (sensitivities) of 7.5e-3 (inner analyzer) and 1.0e-2 (outer analyzer) cm-2 str-1, respectively. However, it is not apparent that these characteristics of the analyzer is really appropriate for the experiment. And there are some

Weak-beam scanning transmission electron microscopy for quantitative dislocation density measurement in steels.

PubMed

Yoshida, Kenta; Shimodaira, Masaki; Toyama, Takeshi; Shimizu, Yasuo; Inoue, Koji; Yoshiie, Toshimasa; Milan, Konstantinovic J; Gerard, Robert; Nagai, Yasuyoshi

2017-04-01

To evaluate dislocations induced by neutron irradiation, we developed a weak-beam scanning transmission electron microscopy (WB-STEM) system by installing a novel beam selector, an annular detector, a high-speed CCD camera and an imaging filter in the camera chamber of a spherical aberration-corrected transmission electron microscope. The capabilities of the WB-STEM with respect to wide-view imaging, real-time diffraction monitoring and multi-contrast imaging are demonstrated using typical reactor pressure vessel steel that had been used in an European nuclear reactor for 30 years as a surveillance test piece with a fluence of 1.09 × 1020 neutrons cm-2. The quantitatively measured size distribution (average loop size = 3.6 ± 2.1 nm), number density of the dislocation loops (3.6 × 1022 m-3) and dislocation density (7.8 × 1013 m m-3) were carefully compared with the values obtained via conventional weak-beam transmission electron microscopy studies. In addition, cluster analysis using atom probe tomography (APT) further demonstrated the potential of the WB-STEM for correlative electron tomography/APT experiments. © The Author 2017. 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.

Additive effects of electronic and nuclear energy loss in irradiation-induced amorphization of zircon

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