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Leon Sanche - One of the best experts on this subject based on the ideXlab platform.
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Absolute vibrational excitation cross sections for 1-18 Ev Electron scattering from condensed dimethyl phosphate (DMP).
The Journal of chemical physics, 2017Co-Authors: V. Lemelin, Andrew D. Bass, J. R. Wagner, Leon SancheAbstract:Absolute cross sections (CSs) for vibrational excitation by 1-18 Ev Electrons incident on condensed dimethyl phosphate (DMP) were measured with a high-resolution Electron energy loss (EEL) spectrometer. Absolute CSs were extracted from EEL spectra of DMP condensed on multilayer film of Ar held at about 20 K under ultra-high vacuum (∼1 × 10−11 Torr). Structures observed in the energy dependence of the CSs around 2, 4, 7, and 12 Ev were compared with prEvious results of gas- and solid-phase experiments and with theoretical studies on dimethyl phosphate and related molecules. These structures were attributed to the formation of shape resonances.
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Unified Mechanism for the Generation of Isolated and Clustered DNA Damages by a Single Low Energy (5–10 Ev) Electron
The Journal of Physical Chemistry C, 2017Co-Authors: Yu Shao, Yi Zheng, Yanfang Dong, Darel J. Hunting, Leon SancheAbstract:Clustered DNA damages are the most detrimental modifications induced by ionizing radiation in cells and sEveral mechanisms have been proposed for their formation. We report measurements of such damages induced by a single low energy Electron via the formation of the two major core-excited resonances of DNA located at 4.6 and 9.6 Ev. Cross-links and single and double strand breaks (SSBs and DSBs) are analyzed by gel electrophoresis. Treatment of irradiated samples with Esherichia coli base excision repair endonucleases rEveals base damages (BDs). DSBs resulting from such treatments arise from clustered damages consisting of at least two BDs or one BD accompanied by a SSB. The total DNA damages induced by 4.6 and 9.6 Ev Electrons are 132 ± 32 and 201 ± 36 × 10–15 Electron–1 molecule–1, comprising 43% and 52% BDs, respectively. We propose a unifying mechanism to account for these clustered damages, DSBs, and single BDs, as well as all prEviously measured isolated lesions.
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Absolute vibrational cross sections for 1-19 Ev Electron scattering from condensed tetrahydrofuran (THF)
The Journal of chemical physics, 2016Co-Authors: V. Lemelin, Pierre Cloutier, Andrew D. Bass, Leon SancheAbstract:Absolute cross sections (CSs) for vibrational excitation by 1–19 Ev Electrons impacting on condensed tetrahydrofuran (THF) were measured with a high-resolution Electron energy loss spectrometer. Experiments were performed under ultra-high vacuum (3 × 10−11 Torr) at a temperature of about 20 K. The magnitudes of the vibrational CSs lie within the 10−17 cm2 range. Features observed near 4.5, 9.5, and 12.5 Ev in the incident energy dependence of the CSs were compared to the results of theoretical calculations and other experiments on gas and solid-phase THF. These three resonances are attributed to the formation of shape or core-excited shape resonances. Another maximum observed around 2.5 Ev is not found in the calculations but has been observed in gas-phase studies; it is attributed to the formation of a shape resonance.
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Correlation between energy deposition and molecular damage from Auger Electrons: A case study of ultra-low energy (5-18 Ev) Electron interactions with DNA.
Medical physics, 2014Co-Authors: Mohammad Rezaee, Darel J. Hunting, Leon SancheAbstract: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 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{sup 125}I within DNA, the Auger Electrons of 5–18 Ev deposit the energies of 12.1 and 9.1more » 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 (
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Damage to amino acid-nucleotide pairs induced by 1 Ev Electrons.
Physical chemistry chemical physics : PCCP, 2010Co-Authors: Sylwia Ptasinska, Nigel J. Mason, Leon SancheAbstract:We have investigated the role of two selected amino acids, glycine and arginine, on damage induced to a short chain of single stranded DNA, the tetramer GCAT, during 1 Ev Electron exposure. At this energy, DNA has a high cross section for DNA damage via exclusively dissociative Electron attachment. Surprisingly, at low ratios of glycine:GCAT, an increase in the total fragmentation yield is observed, whilst at higher ratios, glycine and arginine appear to protect DNA from the direct action of Electrons. In addition, binding energies were calculated by molecular modelling of the interactions between these amino acids and either nucleobases or nucleotides. These binding energies appear to be related to the ability of amino acids to protect DNA against low energy Electron damage.
L. Sanche - One of the best experts on this subject based on the ideXlab platform.
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effective and absolute cross sections for low energy 1 30 Ev Electron interactions with condensed biomolecules
Applied physics reviews, 2018Co-Authors: Yi Zheng, L. SancheAbstract:Ionizing radiation is intensively used for therapeutic [e.g., radiotherapy, brachytherapy, and targeted radionuclide therapy (TRT)], as well as for diagnostic medical imaging purposes. In these applications, the radiation dose given to the patient should be known and controlled. In conventional cancer treatments, absorbed dose calculations rely essentially on scattering cross sections (CSs) of the primary high-energy radiation. In more sophisticated treatments, such as combined radio- and chemo-therapy, a description of the details of energy deposits at the micro- and nano-scopic lEvel is preferred to relate dose to radiobiological effectiveness or to Evaluate doses at the biomolecular lEvel, when radiopharmaceuticals emitting short-range radiation are delivered to critical molecular components of cancer cells (e.g., TRT). These highly radiotoxic compounds emit large densities of low-energy Electrons (LEEs). More generally, LEE (0-30 Ev) are emitted in large numbers by any type of high-energy radiation; i.e., about 30 000 per MEv of deposited primary energy. Thus, to optimize the effectiveness of sEveral types of radiation treatments, the energy deposited by LEEs must be known at the lEvel of the cell, nucleus, chromosome, or DNA. Such local doses can be Evaluated by Monte Carlo (MC) calculations, which account Event-by-Event, for the slowing down of all generations of particles. In particular, these codes require as input parameters absolute LEE CSs for elastic scattering, energy losses, and direct damage to vital cellular molecules, particularly DNA, the main target of radiation therapy. In the last decade, such CSs have emerged in the literature. Furthermore, a method was dEveloped to transform relative yields of damages into absolute CSs by measuring specific parameters in the experiments. In this rEview article, we first present a general description of dose calculations in biological media via MC simulation and give an overview of the CSs available from theoretical calculations and gas-phase experiments. The properties of LEE scattering in the gas-phase are then compared to those in the condensed phase. The remaining portion of the article is dEvoted to condensed-phase CSs. We provide absolute LEE scattering CSs for Electronic, vibrational, and phonon excitation of biomolecules as well as for dissociative Electron attachment, Electron intra- and inter-molecular stabilization, and bond dissociation, including strand breaks and degradation product formation. The biomolecules are O2, CO2, H2O, DNA bases, sugar and phosphate unit analogs, oligonucleotides, plasmid DNA, and the amino acid tryptophan. CSs for strand breaks in radiosensitizing and chemotherapeutic molecules bond or not to a short DNA strand are also listed. The principle of each experimental technique and mathematical methods utilized to generate all condensed-phase CSs are briefly explained. The mechanisms responsible for the magnitudes of the CSs are discussed.
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correlation between energy deposition and molecular damage from auger Electrons a case study of ultra low energy 5 18 Ev Electron interactions with dna
Medical Physics, 2014Co-Authors: Mohammad Rezaee, Darel J. Hunting, L. SancheAbstract: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 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{sup 125}I within DNA, the Auger Electrons of 5–18 Ev deposit the energies of 12.1 and 9.1more » 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 should be considered in the dosimetry calculation of such radionuclides. Moreover, absorbed dose is not an appropriate physical parameter for nanodosimetry. Instead, stopping cross section, which describes the probability of energy deposition in a target molecule can be an appropriate nanodosimetric parameter. The stopping cross section is correlated with a damaging cross section (e.g., cross section for the double-strand break formation) to quantify the number of each specific lesion in a target molecule for each nuclear decay of a single Auger-Electron emitting radionuclide.« less
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nanodosimetry of auger Electrons a case study from the decay of 125 i and 0 18 Ev Electron stopping cross sections of cytosine
Physical Review E, 2013Co-Authors: M Michaud, M Bazin, L. SancheAbstract:Radiopharmaceuticals emitting Auger Electrons are often injected into patients undergoing cancer treatment with targeted radionuclide therapy (TRT). In this type of radiotherapy, the radiation source is radial and most of the emitted primary particles are low-energy Electrons (LEEs) having kinetic energies distributed mostly from zero to a few hundred Electron volts with very short ranges in biological media. These LEEs generate a high density of energy deposits and clustered damage, thus offering a relative biological effectiveness comparable to that of alpha particles. In this paper, we present a simple model and corresponding measurements to assess the energy deposited near the site of the radiopharmaceuticals in TRT. As an example, a calculation is performed for the decay of a single ${}^{125}$I radionuclide surrounded by a 1-nm-radius spherical shell of cytosine molecules using the energy spectrum of LEEs emitted by ${}^{125}$I along with their stopping cross sections between 0 and 18 Ev. The dose absorbed by the cytosine shell, which occupies a volume of 4 nm${}^{3}$, is extremely high. It amounts to 79 kGy per decay of which 3$%$, 39$%$, and 58$%$ is attributed to vibrational excitations, Electronic excitations, and ionization processes, respectively.
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Alteration of Protein Constituents Induced by Low-Energy (
The Journal of Physical Chemistry B, 2004Co-Authors: H. Abdoul-carime, L. SancheAbstract:We report mass spectrometric measurements of anions desorbed by 1−40 Ev Electron impact on thin films of glycine (Gly), alanine (Ala) and cysteine (Cys) physisorbed on a Pt substrate. (H-, CH-, CH2...
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Mechanism for Anion and Sulfur-Radical Production by 1−18 Ev Electron Impact on Dimethyl Disulfide Adsorbed on Ice
The Journal of Physical Chemistry B, 2002Co-Authors: H. Abdoul-carime And, L. SancheAbstract:We report the 1−18 Ev Electron-stimulated desorption of the anions H-, S-, CH3-, and (SCH3)- from dimethyl disulfide (CH3SSCH3) condensed on amorphous D2O films physisorbed on Pt. Below 11 Ev, the desorbed anions and their respective sulfur-radical counterparts (CH2SSCH3)•, (CH3SCH3), (SSCH3)•, and (SCH3)• are formed via dissociative Electron attachment to CH3SSCH3 (i.e., from the formation and subsequent dissociation of temporary states of CH3SSCH3-). At 4.5, 6.0, and 9.0 Ev incident Electron energies, different dissociative attachment channels compete for the production of these reactive species. Above 11 Ev, the same anions are produced via dipolar dissociation with corresponding cation fragments. A negative species observed at 35 amu is attributed to the formation of long-lived or stable (SHD)- anions, produced via secondary reactions on the ice film. Anion desorption is shown to be enhanced by the presence of the water substrate.
Thomas M. Orlando - One of the best experts on this subject based on the ideXlab platform.
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low energy 5 250 Ev Electron stimulated desorption of h h 2 and h h 2 o n from low temperature water ice surfaces
Physical Review B, 2005Co-Authors: Janine Herringcaptain, Gregory A Grieves, Alex Alexandrov, Matthew T Sieger, Haiyan Chen, Thomas M. OrlandoAbstract:Low-energy $(5--250\phantom{\rule{0.3em}{0ex}}\mathrm{Ev})$ Electron-stimulated desorption (ESD) has been used to study the production and removal of ${\mathrm{H}}^{+}$, $\mathrm{H}_{2}{}^{+}$, and ${\mathrm{H}}^{+}{({\mathrm{H}}_{2}\mathrm{O})}_{n=1--8}$ from porous amorphous solid water (PASW), amorphous solid water (ASW), and crystalline (CI) water ice films. The threshold energies for ESD of ${\mathrm{H}}^{+}$ and $\mathrm{H}_{2}{}^{+}$ from CI and ${\mathrm{H}}^{+}$ and ${\mathrm{H}}^{+}({\mathrm{H}}_{2}\mathrm{O})$ from both PASW and ASW are $\ensuremath{\sim}22\ifmmode\pm\else\textpm\fi{}3\phantom{\rule{0.3em}{0ex}}\mathrm{Ev}$. There is also a $\mathrm{H}_{2}{}^{+}$ yield increase at $\ensuremath{\sim}40\ifmmode\pm\else\textpm\fi{}3\phantom{\rule{0.3em}{0ex}}\mathrm{Ev}$ and a $\ensuremath{\sim}70\ifmmode\pm\else\textpm\fi{}3\phantom{\rule{0.3em}{0ex}}\mathrm{Ev}$ threshold for ESD of ${\mathrm{H}}^{+}{({\mathrm{H}}_{2}\mathrm{O})}_{n=2--8}$ for all phases of ice. $\mathrm{H}_{2}{}^{+}$ production and desorption involves direct molecular elimination and reactive scattering of an energetic proton. Both of these channels likely involve localized two-hole one-Electron and∕or two-hole final states containing $4{a}_{1}$, $3{a}_{1}$, and∕or $2{a}_{1}$ character. The $70\phantom{\rule{0.3em}{0ex}}\mathrm{Ev}$ cluster ion threshold implicates either an initial $(2a_{1}{}^{\ensuremath{-}2})$ state localized on a monomer or the presence of at least two neighboring water molecules each containing a single hole. The resulting correlated two-hole or two-hole, one-Electron configurations are localized within a complex and result in an intermolecular Coulomb repulsion and cluster ion ejection. The ${\mathrm{H}}^{+}{({\mathrm{H}}_{2}\mathrm{O})}_{n}$ yields are highest from PASW relative to ASW and CI and decrease with temperature, whereas the $\mathrm{H}_{2}{}^{+}$ yields are highest for CI and increase with temperature. The temperature effects and cluster ion distributions are accounted for by distance and temperature dependent hole screening. Changes in screening, hole lifetimes and hopping probabilities are greatest for ${a}_{1}$ lEvels. This is supported by valence band photoemission studies of ice as a function of temperature.
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thermal and radiation stability of the hydrated salt minerals epsomite mirabilite and natron under europa environmental conditions
Journal of Geophysical Research, 2001Co-Authors: Thomas B. Mccord, Thomas M. Orlando, Glenn Teeter, M. T. Sieger, Nikolay G. Petrik, G B Hansen, Lisa Van KeulenAbstract:We report studies on the thermal and radiolytic stability of the hydrated salt minerals epsomite (MgSO4·7H2O), mirabilite (Na2SO4·10H2O), and natron (Na2CO3·10H2O) under the low-temperature and ultrahigh vacuum conditions characteristic of the surface of the Galilean satellite Europa. We prepared samples, ran temperature-programmed dehydration (TPD) profiles and irradiated the samples with Electrons. The TPD profiles are fit using Arrhenius-type first-order desorption kinetics. This analysis yields activation energies of 0.90±0.10, 0.70±0.07, and 0.45±0.05 Ev for removal of the hydration water for epsomite, natron, and mirabilite, respectively. A simple extrapolation indicates that at Europa surface temperatures (<130 K), epsomite should remain hydrated over geologic timescales (∼1011–1014 years), whereas natron and mirabilite may dehydrate appreciably in approximately 108 and 103 years, respectively. A small amount of SO2 was detected during and after 100 Ev Electron-beam irradiation of dehydrated epsomite and mirabilite samples, whereas products such as O2 remained below detection limits. The upper limit for the 100 Ev Electron-induced damage cross section of mirabilite and epsomite is ∼10−19 cm2. The overall radiolytic stability of these minerals is partially due to (1) the multiply charged nature of the sulfate anion, (2) the low probability of rEversing the attractive Madelung (mostly the attractive electrostatic) potential via Auger decay, and (3) solid-state caging effects. Our laboratory results on the thermal and radiolytic stabilities of these salt minerals indicate that hydrated magnesium sulfate and perhaps other salts could exist for geologic timescales on the surface of Europa.
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The role of excitons and substrate temperature in low-energy (5–50 Ev) Electron-stimulated dissociation of amorphous D2O ice
Surface Science, 1997Co-Authors: Thomas M. Orlando, Greg A. KimmelAbstract:Abstract We have studied the interaction of low-energy (5–50 Ev) Electrons with nanoscale (∼10 ML) ice films by probing the yields and quantum-state distributions of the neutral dissociation products using laser resonance-enhanced multiphoton ionization spectroscopy. In particular, we have observed the Electron-stimulated desorption (ESD) of D (2S), O (3P2) and O (1D2) from amorphous D2O films. These products are observed at threshold energies (relative to the vacuum lEvel) between ∼6.5–7 Ev and desorb with low kinetic energies (∼60–85 mEv) which are independent of the incident Electron energy. We associate the ESD of atomic fragments from ice with dissociation of Frenkel-type excitons of 4a1 character which are near the bottom of the ice conduction band. These excitons are created either directly or via Electron-ion recombination. Changing the surface temperature from 88 to 145 K results in an increase in the thermal component of the time-of-flight (kinetic energy) distributions and an overall increase in the neutral fragment yield. We suggest that the change in neutral yield with substrate temperature results from a combination of: (1) increased Electron-ion recombination; (2) exciton transport to the near-surface region; and (3) dissociation followed by inelastic scattering and desorption.
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Observation of Negative Ion Resonances in Amorphous Ice via Low-Energy (5-40 Ev) Electron-Stimulated Production of Molecular Hydrogen.
Physical review letters, 1996Co-Authors: Greg A. Kimmel, Thomas M. OrlandoAbstract:The {ital D}{sub 2}({sup 1}{Sigma}{sup +}{sub {ital g}}, {ital v}=0{endash}2, {ital J}=0{endash}2) desorbates produced during low-energy (5{endash}40 Ev) Electron-beam irradiation of amorphous D{sub 2}O ice were monitored using resonance-enhanced laser ionization spectroscopy. We attribute the structure in the D{sub 2} yield as a function of the incident Electron energy to core-excited negative ion resonances. These resonances, or the excited states produced after Electron autodetachment, decay via molecular elimination to yield {ital D}{sub 2}({sup 1}{Sigma}{sup +}{sub {ital g}}) directly. D{sub 2} is observed with {ital v}=0 or 2 but not {ital v}=1, suggesting a symmetry propensity in the excitation or decay of the resonances. {copyright} {ital 1996 The American Physical Society.}
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Low-energy (5-120 Ev) Electron-stimulated dissociation of amorphous D2O ice: D(2S), O(3P2,1,0), and O(1D2) yields and velocity distributions.
Physical review letters, 1995Co-Authors: Greg A. Kimmel, Thomas M. OrlandoAbstract:Laser resonance enhanced multiphonon ionization spectroscopy was used to measure yields and velocity distributions of the D $(^{2}S)$, O $(^{3}P_{2,1,0})$, and $\mathrm{O}(^{1}D_{2})$ produced during low-energy (5--120 Ev) Electron-beam irradiation of amorphous ${\mathrm{D}}_{2}$O ice. Electron-stimulated dissociation has a very low energy threshold ( $\ensuremath{\sim}$6--7 Ev), and the neutral fragments desorb with low kinetic energies ( $\ensuremath{\sim}$60--85 mEv) which are independent of the incident Electron energy. The data suggest that desorption of neutral fragments results from dissociation of excited states formed directly or via Electron-ion recombination.
Xueguang Ren - One of the best experts on this subject based on the ideXlab platform.
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experimental and theoretical triple differential cross sections for tetrahydrofuran ionized by low energy 26 Ev Electron impact
Physical Review A, 2016Co-Authors: Esam Ali, Alexander Dorn, Xueguang Ren, Chuangang Ning, J Colgan, Don H. MadisonAbstract:We report an experimental and theoretical study of low-energy Electron-impact ionization of tetrahydrofuran, which is a molecule of biological interest. The experiments were performed using an advanced reaction microscope specially built for Electron-impact ionization studies. The theoretical calculations were performed within the molecular three-body distorted-wave model. Reasonably good agreement is found between experiment and theory.
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Low-energy (E-0=65 Ev) Electron-impact ionization of neon: Internormalized triple-differentical cross sections in 3D kinematics
Journal of Physics: Conference Series, 2015Co-Authors: Xueguang Ren, Don H. Madison, Klaus Bartschat, Thomas Pflüger, Sadek Amami, Oleg Zatsarinny, Marvin Weyland, Woon Yong Baek, Hans Rabus, Alexander DornAbstract:We present a combined experimental and theoretical study on the low-energy (E0 = 65 Ev) Electron- impact ionization of neon. The experimental data are compared to predictions from a hybrid second-order distorted-wave Born plus R-matrix approach (DWB2-RM), the distorted-wave Born approximation with inclusion of post-collision interaction (DWBA-PCI), a three-body distorted-wave approach (3DW), and a B-spline R-matrix (BSR) with pseudostates approach. Excellent agreement is found between experiment and the 3DW and BSR theories. The importance of PCI effects is clearly visible in this low-energy Electron-impact ionization process.
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high resolution e 2e ion study of Electron impact ionization and fragmentation of methane
Journal of Chemical Physics, 2015Co-Authors: J. Ullrich, Xueguang Ren, Thomas Pflüger, Marvin Weyland, Woon Yong Baek, Hans Rabus, Alexander DornAbstract:The ionization and fragmentation of methane induced by low-energy (E0 = 66 Ev) Electron-impact is investigated using a reaction microscope. The momentum vectors of all three charged final state particles, two outgoing Electrons, and one fragment ion, are detected in coincidence. Compared to the earlier study [Xu et al., J. Chem. Phys. 138, 134307 (2013)], considerable improvements to the instrumental mass and energy resolutions have been achiEved. The fragment products CH4 (+), CH3 (+), CH2 (+), CH(+), and C(+) are clearly resolved. The binding energy resolution of ΔE = 2.0 Ev is a factor of three better than in the earlier measurements. The fragmentation channels are investigated by measuring the ion kinetic energy distributions and the binding energy spectra. While being mostly in consistence with existing photoionization studies the results show differences including missing fragmentation channels and prEviously unseen channels.
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an e 2e ion study of low energy Electron impact ionization and fragmentation of tetrahydrofuran with high mass and energy resolutions
Journal of Chemical Physics, 2014Co-Authors: J. Ullrich, Xueguang Ren, Thomas Pflüger, Marvin Weyland, Hans Rabus, Woon Yoon Baek, Alexander DornAbstract:We study the low-energy (E0 = 26 Ev) Electron-impact induced ionization and fragmentation of tetrahydrofuran using a reaction microscope. All three final-state charged particles, i.e., two outgoing Electrons and one fragment ion, are detected in triple coincidence such that the momentum vectors and, consequently, the kinetic energies for charged reaction products are determined. The ionic fragments are clearly identified in the experiment with a mass resolution of 1 amu. The fragmentation pathways of tetrahydrofuran are investigated by measuring the ion kinetic energy spectra and the binding energy spectra where an energy resolution of 1.5 Ev has been achiEved using the recently dEveloped photoemission Electron source. Here, we will discuss the fragmentation reactions for the cations C4H8O+, C4H7O+, C2H3O+, C3H6+, C3H5+, C3H3+, CH3O+, CHO+, and C2H3+.
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3D-cross sections for argon single ionization by 200 Ev Electron impact
Journal of Physics: Conference Series, 2009Co-Authors: Xueguang Ren, Alexander Dorn, Klaus Bartschat, Arne Senftleben, Thomas Pflüger, Joachim UllrichAbstract:Using a multi-particle momentum spectrometer (reaction microscope), three-dimensional and fully differential cross sections for Electron impact ionization were obtained, providing benchmark data for comprehensive tests of theoretical calculations. Since all final-state particles, including the scattered projectile were detected, a good momentum transfer resolution was obtained also for heavy targets like argon. Results for ionization of the 3p-orbital in Argon by 200 Ev Electron impact are presented. The cross section patterns display rich structure, which are partially reproduced by theory, although differences persist outside the projectile scattering plane.
Julien Pernot - One of the best experts on this subject based on the ideXlab platform.
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oxygen vacancy and ec 1 Ev Electron trap in zno
Journal of Physics D, 2014Co-Authors: Julien Pernot, Gauthier Chicot, Jean-louis Santailler, Guy Feuillet, P MuretAbstract:Fourier transform deep lEvel transient spectroscopy has been performed between 80 and 550 K in five n-type ZnO samples grown by different techniques. The capture cross section and ionization energy of four Electron traps have been deduced from Arrhenius diagrams. A trap 1 Ev below the conduction band edge is systematically observed in the five samples with a large apparent capture cross section for Electrons (1.6 ± 0.4 × 10−13 cm2) indicating a donor character. The assignment of this deep lEvel to the oxygen vacancy is discussed on the basis of available theoretical predictions.
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Oxygen vacancy and EC − 1 Ev Electron trap in ZnO
Journal of Physics D: Applied Physics, 2014Co-Authors: Gauthier Chicot, Pierre Muret, Jean-louis Santailler, Guy Feuillet, Julien PernotAbstract:Fourier transform deep lEvel transient spectroscopy has been performed between 80 and 550 K in five n-type ZnO samples grown by different techniques. The capture cross section and ionization energy of four Electron traps have been deduced from Arrhenius diagrams. A trap 1 Ev below the conduction band edge is systematically observed in the five samples with a large apparent capture cross section for Electrons (1.6 ± 0.4 × 10−13 cm2) indicating a donor character. The assignment of this deep lEvel to the oxygen vacancy is discussed on the basis of available theoretical predictions.
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Electronic properties of the EC-0.6 Ev Electron trap in n-type GaN
Journal of Applied Physics, 2008Co-Authors: Julien Pernot, Pierre MuretAbstract:The Electronic properties of the EC-0.6 Ev Electron trap in n-type GaN are investigated by deep-lEvel transient spectroscopy with the help of an experimental method relying on space-charge depth modulation [D. Pons, J. Appl. Phys. 55, 3644 (1984)]. The free energy and capture cross-section temperature dependence are determined between 250 and 330 K. The capture cross section is found at σn=8×10−16 cm2, corresponding to a neutral center with a degeneracy factor of gn≤4.
