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Resistência e tolerância a impacto transversal de baixa energia de um laminado híbrido metal/fibra; Low-energy transverse impact resistance and tolerance of hybrid fiber/metal laminate

GUALBERTO, A.R.M.; GATT, M.C.A.; TARPANI, J.R.
Fonte: Rede Latino-Americana de Materiais Publicador: Rede Latino-Americana de Materiais
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
67.388027%
A energia absorvida no impacto transversal do laminado híbrido metal/fibra Glare® foi determinada por três diferentes métodos. O primeiro método utiliza um sofisticado aparato Laser-Doppler que registra a aceleração e a desaceleração do impactador ao longo do evento de choque mecânico por queda-de-peso, enquanto que o segundo se baseia apenas nos dados de carga de impacto contra o tempo de contato do impactador com o espécime. Já o terceiro método considera somente as velocidades do impactador pré- e pós-impacto. Concluiu-se que as duas primeiras metodologias geram resultados bastante similares entre si, com o material em geral absorvendo cerca de 70% da energia disponibilizada no impacto, enquanto que a terceira abordagem apresentou resultados excessivamente não-conservadores. As propriedades residuais em flexão dos laminados previamente danificados por impacto demonstraram que o módulo de elasticidade é o parâmetro mais confiável para a monitoração do grau de integridade estrutural do compósito híbrido.; The absorbed energy during the low-velocity transversal impact of hybrid metal/fiber GlareTM laminate was determined by three different analytical methods. The first method employs a sophisticated Laser-Doppler apparatus that registers the acceleration and deceleration of the impact tup along the drop-weight test...

Caracterização de danos e resistência residual de um laminado híbrido metal/fibra após impactos repetidos de baixa energia; Damage characterization and residual resistance of fiber/metal laminate after low energy repeated impact

TARPANI, J.R.; CARDOSO, F.L.A; GUALBERTO, A.R.M.; GATTI, M.C.A.
Fonte: Rede Latino-Americana de Materiais Publicador: Rede Latino-Americana de Materiais
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
57.28099%
A energia absorvida pelo laminado metal/fibra Glare® durante impactos repetidos de baixa energia aplicados segundo três diferentes sequências de carregamento dinâmico foi determinada através de um aparato Laser-Doppler. Os resultados indicaram que a energia absorvida (Ea) foi cerca de 40% da energia total disponibilizada (Et = 6 Joules), independentemente da sequência de impactos empregada. As propriedades mecânicas residuais do laminado em condições de flexão monotônica sob três pontos, assim como os danos visualmente detectáveis criados por impacto no material, também não revelaram efeitos significativos da história de cargas dinâmicas experimentada pelo laminado híbrido.; The energy absorbed by the fiber/metal laminate GlareTM during low-energy repeated impact events according to three different dynamic loading sequences has been determined using a Laser-Doppler apparatus. The results indicated that the absorbed energy (Ea) was approximately 40% of the total available energy (Et = 6 Joules) regardless of the impact sequence applied. The residual mechanical properties of the laminate under three-point flexural conditions, as well as the visually detectable damage created by impact on the material, did not show any significant effect of the dynamic loading sequence withstood by the hybrid laminate.

Failure analysis of low velocity impact on thin composite laminates: Experimental and numerical approaches

TITA, Volnel; CARVALHO, Jonas de; VANDEPITTE, Dirk
Fonte: ELSEVIER SCI LTD Publicador: ELSEVIER SCI LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
67.252783%
The dynamic behavior of composite laminates is very complex because there are many concurrent phenomena during composite laminate failure under impact load. Fiber breakage, delaminations, matrix cracking, plastic deformations due to contact and large displacements are some effects which should be considered when a structure made from composite material is impacted by a foreign object. Thus, an investigation of the low velocity impact on laminated composite thin disks of epoxy resin reinforced by carbon fiber is presented. The influence of stacking sequence and energy impact was investigated using load-time histories, displacement-time histories and energy-time histories as well as images from NDE. Indentation tests results were compared to dynamic results, verifying the inertia effects when thin composite laminate was impacted by foreign object with low velocity. Finite element analysis (FEA) was developed, using Hill`s model and material models implemented by UMAT (User Material Subroutine) into software ABAQUS (TM), in order to simulate the failure mechanisms under indentation tests. (C) 2007 Elsevier Ltd. All rights reserved.

Low energy elastic and electronically inelastic electron scattering from biomolecules.

Costa, Romarly F. da; Bettega, Marcio Henrique Franco; Varella, Marcio Teixeira do Nascimento; Lopes, Maria C. A.; Khakoo, Murtadha A.; Hargreaves, Leigh R.; Serna, Gabriela; Lima, Marco A. P.
Fonte: Águas de Lindóia Publicador: Águas de Lindóia
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
66.853296%
Reactions initiated by collisions with low-energy secondary electrons has been found to be the prominent mechanism toward the radiation damage on living tissues through DNA strand breaks. Now it is widely accepted that during the interaction with these secondary species the selective breaking of chemical bonds is triggered by dissociative electron attachment (DEA), that is, the capture of the incident electron and the formation of temporary negative ion states [1,2,3]. One of the approaches largely used toward a deeper understanding of the radiation damage to DNA is through modeling of DEA with its basic constituents (nucleotide bases, sugar and other subunits). We have tried to simplify this approach and attempt to make it comprehensible at a more fundamental level by looking at even simple molecules. Studies involving organic systems such as carboxylic acids, alcohols and simple ¯ve-membered heterocyclic compounds are taken as starting points for these understanding. In the present study we investigate the role played by elastic scattering and electronic excitation of molecules on electron-driven chemical processes. Special attention is focused on the analysis of the in°uence of polarization and multichannel coupling e®ects on the magnitude of elastic and electronically inelastic cross-sections. Our aim is also to investigate the existence of resonances in the elastic and electronically inelastic channels as well as to characterize them with respect to its type (shape...

Dano em placas laminadas devido ao impacto a baixas velocidades.; Damage in laminate plates caused by low velocity impact.

Romariz, Luiz André
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 22/08/2008 PT
Relevância na Pesquisa
57.08237%
Materiais compósitos laminados possuem uma alta eficiência estrutural, mas que é comprometida pela baixa resistência a cargas de impacto. O objetivo deste trabalho é o desenvolvimento de uma metodologia de simulação numérica para a estimativa de danos causados por cargas de impacto a baixas velocidades em placas de material compósito laminado. Ensaios experimentais foram realizados em placas reforçadas com tecidos de fibra de carbono e matriz de resina epóxi. Foram avaliadas três espessuras. Os carregamentos de impacto com uma massa em queda livre foram pontuais e transversais à placa, com intervalos de energia variando entre 5J e 94J, com velocidades inferiores a 6 m/s. As simulações numéricas utilizaram um programa comercial de elementos finitos com integração explícita. Foram avaliados dois critérios de falha da lâmina. O primeiro é o critério de máxima tensão. O segundo é uma proposta de modificação no critério de falha de Hashin, para sua aplicação em laminados reforçados com tecidos bidirecionais. Também foram avaliados quatro diferentes critérios de degradação da lâmina. As evoluções das forças de contato entre o impactador e a placa foram muito bem representadas numericamente. As áreas e os comprimentos dos danos numéricos foram similares ou maiores que os medidos nos resultados experimentais.; Laminate composite materials have high structural efficiency...

Metodologias para a determinação das propriedades de impacto de baixa energia de laminados metal-fibra; Methodologies to determine low-energy impact properties of fiber-metal laminates

Gualberto, Alan Rodrigo Marinho
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 13/06/2008 PT
Relevância na Pesquisa
77.47964%
Aplicações dos laminados híbridos metal-fibra incluem, além da indústria aeronáutica, as indústrias naval e automobilística. Diferentemente do setor aeronáutico, pesquisas sobre impactos mecânicos nas duas outras áreas da mobilidade são freqüentemente limitadas pela disponibilidade de equipamentos laboratoriais, de modo que é desejável o desenvolvimento de procedimentos de baixo custo para a determinação da resistência e tolerância a danos por impacto dos materiais de construção. Neste trabalho, a resistência a danos por impacto transversal do laminado híbrido metal-fibra Glare-5® foi determinada via três diferentes metodologias. A primeira utiliza um aparato sofisticado aparato Laser-Doppler para monitorar a aceleração e desaceleração de um impactador esférico de aço com 5 mm de diâmetro durante o evento do choque mecânico. O segundo método se baseia apenas nos valores de carga (força aplicada) vs. o tempo de impacto para a obtenção da energia absorvida pelo material. O terceiro considera somente os dados da velocidade do impactador, ou projétil, imediatamente antes e após o impacto. Concluiu-se que os valores de energia obtidos segundo as duas primeiras metodologias são similares, com o Laser-Doppler gerando resultados levemente não-conservadores...

Monitoramento de integridade estrutural de materiais compostos sujeitos a impactos empregando a técnica da impedância eletromecânica; Structural health monitoring of composite materials subjected to impacts using the electromechanical impedance technique

Tsuruta, Karina Mayumi
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Dissertação
POR
Relevância na Pesquisa
67.373354%
Atualmente, os materiais compostos vêm substituindo os materiais tradicionais, principalmente em aplicações que exigem melhor desempenho, segurança, economia e durabilidade. No entanto, estes materiais apresentam mecanismos de dano complexos que podem ser difíceis de detectar em estágios iniciais. Os danos podem ocorrer durante a fabricação ou utilização, ou mesmo durante a manutenção. Em estruturas aeronáuticas, as maiores causas de dano estão ligadas a objetos que colidem com a estrutura, como a colisão de pássaros, granizo, pedras na pista de pouso/decolagem e por ferramentas durante a manutenção. Em vista disto, é grande o interesse em detectar danos incipientes provocados por impactos em componentes estruturais constituídos de materiais compostos. Neste contexto, o objetivo deste trabalho é o de avaliar o uso de uma técnica de monitoramento de integridade estrutural baseada no conceito de impedância eletromecânica para a detecção e quantificação de danos causados por impactos de baixa energia em placas de material composto. O método da impedância eletromecânica é uma técnica não destrutiva que utiliza o acoplamento eletromecânico de materiais piezelétrico colados à superficie da estrutura monitorada. A metodologia adotada consiste em realizar impactos em corpos de prova de materiais compostos empregando um dispositivo pendular ad hoc que permite obter diversos valores da energia de impacto. Para cada corpo de prova...

Differential cross sections in pi^+- p scattering at low energies; Differentielle Wirkungsquerschnitte in der pi^+- p Streuung bei niedrigen Energien

Denz, Holger
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
EN
Relevância na Pesquisa
57.01277%
The pion-nucleon sigma term, which is an important parameter in chiral perturbation theory and a measure of explicit chiral symmetry breaking of QCD due to non-vanishing current quark masses, can be extracted from elastic pi p scattering data using partial wave analyses and dispersion relations. However, results of recent analyses yield a very large value for the sigma term, which leads to problems with the interpretation. Since the quality of the database on which the extraction is based is crucial for the result and there are known problems with incompatible measurements and scarce low energy data available, a new experiment was carried out within the CHAOS collaboration. Using the CHAOS detector and a newly developed range telescope covering the extreme forward scattering angles, differential cross sections in pi^+- p elastic scattering were measured at 19.9, 25.8, 32.0, 37.1, 43.3, 57.0 and 67.0 MeV pion kinetic energy at the TRIUMF meson factory in Vancouver, Canada. The CHAOS detector consists of tracking chambers and particle identification counters in a vertical magnetic field geometry. This experimental arrangement allows simultaneous measurements over a large angular range from 10 to 170 degrees, thus reducing systematic errors. Well-known mu^+- p scattering cross sections at forward angles were measured simultaneously as a check of the angle reconstruction and normalization. This thesis describes the analysis of the low energy data from 19.9 to 43.3 MeV. Typical relative errors for the data are about 3 % statistical error per data point and between 3 and 8 % systematic error for the data sets. For pi^- p elastic scattering...

Development of an advanced low energy focused ion beam system based on immersion optics; Entwicklung einer verbesserten niederenergetischen Rasterionensonde mit Immersionsoptik

Rauscher, Michael
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
EN
Relevância na Pesquisa
56.98654%
In this study an advanced approach towards low energy focused ion beam (FIB) system design and operation based on the use of immersion optics is presented. The system performance in terms of obtainable resolution for a given beam current has been investigated both theoretically as well as experimentally using a newly developed ion beam column. A thorough aberration-optical analysis has been carried out, which comprised the calculation of first-order optical properties and aberration coefficients of individual optical components as well as of the overall system. The results of this analysis have been used as a guideline for the layout and the choice of the favourable operation mode of the experimental test setup. Additionally, the impact of mutual Coulomb interactions on the thus predicted system performance has also been considered using numerical simulation tools. Methods have been developed to provide an objective measure for quantifying these interaction effects, and it has been shown that the latter may indeed be considered to have a limiting influence for the achievable probe size in the experimental setup. In parallel to these theoretical investigations, the practical realisation of the ion beam system was initiated. A reliably operating ion beam column has been developed...

Low energy impact loading of graphite-epoxy plates.

Ferris, Richard Lee
Fonte: Monterey, California: Naval Postgraduate School Publicador: Monterey, California: Naval Postgraduate School
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
67.20247%
An experimental and theoretical analysis was performed on low energy impact loading of thin (.040 inches) graphite-epoxy plates. Six-inch square plates were subjected to dynamic impact (below the ballistic range) and static loading. The plate static strain energy and dynamic impact energy for failure were equal and constant. Theoretical analysis was performed using both exact and finite element methods. Small deflection theory was assumed and found to be inapplicable; the plates behaved in a manner indicating that a large deflection theoretical model would be more appropriate. (Author)

Effect of block copolymer nano-reinforcements on the low velocity impact response of sandwich structures

RAMAKRISHNAN, Karthik Ram; GUERARD, Sandra; VIOT, Philippe; SHANKAR, Krishna
Fonte: Elsevier Publicador: Elsevier
EN
Relevância na Pesquisa
67.15806%
Sandwich composites with fibre reinforced plastic (FRP) facesheets have emerged as a major class of lightweight structural materials in a wide range of engineering fields including aerospace, automotive and marine structures. This is due to attractive mechanical properties such as high specific stiffness and high strength. However, sandwich structures are susceptible to damage caused by impact. The objective of this paper is to evaluate the dynamic response of sandwich composites based on Kevlar fibre reinforced epoxy and Rohacell foam. The improvement in impact performance of these sandwich structures that can be achieved by the addition of nanoparticles in the resin matrix is investigated. Nanostrength, an acrylate triblock copolymer that self-assembles in the nanometer scale is added to the epoxy matrix. The effect of the nano-reinforcements on flat sandwich plates under low velocity impact is investigated at different scales. An instrumented drop tower setup is used for the low velocity impact tests of the sandwich plates with neat or nano-reinforced epoxy matrix, at different energies. The macroscopic response of the sandwich structure and the microscopic phenomena involved in dissipating the impact energy are identified and compared for sandwich plates with and without nanoparticles.

Effect of the fiber reinforcement on the low energy impact behavior of fabric reinforced resin matrix composite materials

Morais,W. A. de; d'Almeida,J. R. M.; Godefroid,L. B.
Fonte: Associação Brasileira de Engenharia e Ciências Mecânicas - ABCM Publicador: Associação Brasileira de Engenharia e Ciências Mecânicas - ABCM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2003 EN
Relevância na Pesquisa
87.21843%
The influence of the fiber used as reinforcement in resin matrix composite materials submitted to repeated low energy impacts is analyzed. The aramid, glass and carbon fiber composites were submitted to drop weight tests from 0.5m and from 1m. The number of impact events necessary to cause failure was recorded, and the fracture characteristics of each composite were analyzed by optical microscopy and X-rays radiography. The results obtained showed that carbon fiber composites have better performance than the glass and aramid composites. This behavior was partially attributed to the higher elastic energy absorption of carbon fibers that delays the propagation of delamination, and fiber breakage. The failure mode of glass fiber composites was dominated by the higher number of glass fibers per surface area of the composites. The worst behavior shown by aramid composites was attributed to the intrinsic anisotropy of aramid fibers.

Experimental characterization and computational simulations of the low-velocity impact behaviour of polypropylene

Torres, Juan Pablo; Frontini, Patricia Maria; Aretxabaleta, Laurentzi
Fonte: John Wiley & Sons Ltd Publicador: John Wiley & Sons Ltd
Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion Formato: application/pdf
ENG
Relevância na Pesquisa
87.23453%
The objective of this work is to validate predictive models for the simulation of the mechanical response of polypropylene undergoing impact situations. The transferability of material parameters deduced from a particular loading scenario (uniaxial loading) to a different loading situation (multiaxial loading) was studied. The material was modelled with a modified viscoplastic phenomenological model based on the G'Sell–Jonas equation. To perform the numerical simulations, a user-material subroutine (VUMAT) was implemented in the ABAQUS/explicit finite element code. Constitutive parameters for the model were determined from isostrain rate uniaxial tensile impact test data using an inverse calibration technique. In addition, falling-weight low-energy impact tests were performed on disc-shaped specimens at velocities in the range 0.7 to 3.13 m s−1. The model predictions were evaluated by comparison of the experimental and finite element response of the falling-weight impact tests. The G'Sell–Jonas model showed much better predictability than classical elastoplasticity models. It also showed excellent agreement with experimental curves, provided stress-whitening damage observed experimentally was accounted for in the model using an element failure criterion; Fil: Torres...

Low energy impact damage modes in aluminum foam and polymer foam sandwich structures

Compston, Paul; Styles, Millicent; Kalyanasundaram, Shankar
Fonte: Sage Science Press Publicador: Sage Science Press
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
77.08656%
The energy absorption of an aluminum foam sandwich structure and a conventional polymer foam sandwich structure is similar for impacts ranging from 5 to 25 J. The polymer foam-based samples exhibit localized damage in the form of skin fracture and core cr

Physics with a very first low-energy beta-beam

Volpe, Cristina
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 18/10/2005
Relevância na Pesquisa
56.90235%
We describe the importance of having low-energy (10-100 MeV) neutrino beams produced through the decay of boosted radioactive ions (``beta-beams''). We focus on the interest for neutrino-nucleus interaction studies and their impact for astrophysics, nuclear and particle physics. In particular, we discuss the relation to neutrinoless double-beta decay. Finally, we mention the status as far as the feasibility of low-energy beta-beams is concerned.; Comment: 5 pages, 2 figures, Proceedings to NUFACT05, June 21-26, 2005

Neutrino factory in stages: Low energy, high energy, off-axis

Tang, Jian; Winter, Walter
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
57.08388%
We discuss neutrino oscillation physics with a neutrino factory in stages, including the possibility of upgrading the muon energy within the same program. We point out that a detector designed for the low energy neutrino factory may be used off-axis in a high energy neutrino factory beam. We include the re-optimization of the experiment depending on the value of theta_13 found. As upgrade options, we consider muon energy, additional baselines, a detector mass upgrade, an off-axis detector, and the platinum (muon to electron neutrino) channels. In addition, we test the impact of Daya Bay data on the optimization. We find that for large theta_13 (theta_13 discovered by the next generation of experiments), a low energy neutrino factory might be the most plausible minimal version to test the unknown parameters. However, if a higher muon energy is needed for new physics searches, a high energy version including an off-axis detector may be an interesting alternative. For small theta_13 (theta_13 not discovered by the next generation), a plausible program could start with a low energy neutrino factory, followed by energy upgrade, and then baseline or detector mass upgrade, depending on the outcome of the earlier phases.; Comment: 23 pages...

Emission of Low-Energy Photons by Electrons at Electron-Positron and Electron-Ion Colliders with Dense Bunches

Jentschura, U. D.; Kotkin, G. L.; Serbo, V. G.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/01/2009
Relevância na Pesquisa
56.95957%
Usually, the emission of low-energy photons in electron-positron (or electron-ion) bunch collisions is calculated with the same approach as for synchrotron radiation (beamstrahlung). However, for soft photons (E_gamma < E_c where E_c is a critical photon energy), when the coherence length of the radiation becomes comparable to the bunch length, the beamstrahlung approximation becomes invalid. In this paper, we present results of our calculation for this region based on approximation of classical currents. We consider several colliders with dense bunches. The number of low-energy photons dN_gamma emitted by N_e electrons per bunch crossing in the energy interval dE_gamma is dN_gamma = alpha g N_e dE_gamma/E_gamma, where alpha is the fine-structure constant, and the function g, which depends on the bunch parameters, typically is of order unity for modern colliders. In particular, for the ILC, we find that E_c = 83 keV and g=5.5 at a vanishing beam axis displacement, and g=0.88, E_c=0.24 keV for KEKB. We also calculate the specific dependence of dN_gamma on the impact parameter between the two beam axes. In principle, the latter aspect allows for online monitoring of the beam axis displacement.; Comment: 10 pages, RevTex

Ultra low energy results and their impact to dark matter and low energy neutrino physics

Bougamont, E.; Colas, P.; Derre, J.; Giomataris, I.; Gerbier, G.; Gros, M.; Magnier, P.; Navick, X. F.; Salin, P.; Savvidis, I.; Tsiledakis, G.; Vergados, J. D.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/10/2010
Relevância na Pesquisa
57.102334%
We present ultra low energy results taken with the novel Spherical Proportional Counter. The energy threshold has been pushed down to about 25 eV and single electrons are clearly collected and detected. To reach such performance low energy calibration systems have been successfully developed: - A pulsed UV lamp extracting photoelectrons from the inner surface of the detector - Various radioactive sources allowing low energy peaks through fluorescence processes. The bench mark result is the observation of a well resolved peak at 270 eV due to carbon fluorescence which is unique performance for such large-massive detector. It opens a new window in dark matter and low energy neutrino search and may allow detection of neutrinos from a nuclear reactor or from supernova via neutrino-nucleus elastic scattering; Comment: 14 pages,16 figures

Low-energy Positron Interactions with Atoms and Molecules

Surko, Clifford M; Gribakin, G F; Buckman, Stephen
Fonte: Institute of Physics Publishing Publicador: Institute of Physics Publishing
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
66.977715%
This paper is a review of low-energy positron interactions with atoms and molecules. Processes of interest include elastic scattering, electronic and vibrational excitation, ionization, positronium formation and annihilation. An overview is presented of the currently available theoretical and experimental techniques to study these phenomena, including the use of trap-based positron beam sources to study collision processes with improved energy resolution. State-resolved measurements of electronic and vibrational excitation cross sections and measurement of annihilation rates in atoms and molecules as a function of incident positron energy are discussed. Where data are available, comparisons are made with analogous electron scattering cross sections. Resonance phenomena, common in electron scattering, appear to be less common in positron scattering. Possible exceptions include the sharp onsets of positron-impact electronic and vibrational excitation of selected molecules. Recent energy-resolved studies of positron annihilation in hydrocarbons containing more than a few carbon atoms provide direct evidence that vibrational Feshbach resonances underpin the anomalously large annihilation rates observed for many polyatomic species. We discuss open questions regarding this process in larger molecules...

Exchange Effects in Low Energy Electron Impact Ionization of the Inner and Outer Sheels of Argon

Biava, D A; Saha, H P; Engel, E; Dreizler, R.M.; McEachran, Robert; Haynes, M.A.; Lohmann, Birgit; Whelan, C T; Madison, Don Harvey
Fonte: Institute of Physics Publishing Publicador: Institute of Physics Publishing
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
67.428%
First order distorted wave Born approximation (DWBA) triple differential cross sections are reported for low-energy electron-impact ionization of the inner 3s and outer 3p shells of argon. Previous DWBA works have demonstrated that experiment and theory are not in accord for low energy ionization of inert gases and here we investigate the importance of exchange scattering. Different approximations for treating exchange scattering are investigated. It is shown that exchange scattering is particularly important for 3s ionization. Even with a proper treatment of exchange, the first order calculations are still not in satisfactory agreement with experiment. Consequently higher order effects will have to be included to achieve a satisfactory description of the low-energy ionization process. We also investigated both the Hartree-Fock and optimized potential methods for calculating atomic wavefunctions and static potentials and found that both methods produced almost the same cross sections.