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Voici les éléments 21-40 de 83

    • Water-molecule dissociation by proton and hydrogen impactPeer reviewedClosed access 

      2007, LECOINTRE, Julien; Luna, H.; de Barros, A. L. F.; Wyer, J. A.; Scully, S. W. J.; Garcia, P. M. Y.; Sigaud, G. M.; Santos, A. C. F.; Senthil, V.; Shah, M. B.; Latimer, C. J.; Montenegro, E. C., HENALLUX
      Article scientifique
      Time-of-flight-based mass analysis of charged water fragments have been used to measure the dissociative and the nondissociative reaction pathways of water formed during collisions with 15 to 100 keV and 500 to 3500 keV H+ projectiles and with 8 to 100 keV H0 projectiles. The fragmentation pathways resulting from the ionization and the electron capture collisions with the incident H+ and H0 ...

    • Rovibrational analysis of the XUV photodissociation of HeH + ionsPeer reviewedClosed access 

      2011, LECOINTRE, Julien; Loreau, J.; Urbain, X.; Vaeck, N., HENALLUX
      Article scientifique
      We investigate the dynamics of the photodissociation of the helium hydride ion HeH+ by XUV radiation with the aim to establish a detailed comparison with a recent experimental work carried out at the FLASH free electron laser using both vibrationally hot and cold ions. We determine the corresponding rovibrational distributions using a dissociative charge transfer setup and the same source conditions ...

    • Ultrafast Relaxation Dynamics Observed Through Time-Resolved Photoelectron Angular DistributionsPeer reviewedClosed access 

      2010, LECOINTRE, Julien; Roberts, G.M.; Horke, D. A.; Verlet, J.R.R., HENALLUX
      Article scientifique
      Time-resolved photoelectron imaging of the 7,7,8,8-tetracyanoquinodimethane (TCNQ) radical anion is presented. Photoelectron angular distributions (PADs) are qualitatively analyzed in terms of the simple s-p model that is based on symmetry arguments. The internal conversion dynamics from the first excited state (12B3u) to the ground state (2B2g) may be observed through temporal changes in the PADs ...

    • Screening effects and total cross sections of single, double and triple ionization of neon by fast electronsPeer reviewedClosed access 

      2008, LECOINTRE, Julien; Defrance, P.; Jureta, J.J.; Kereselidze, T.; Machavariani, Z.S., HENALLUX
      Article scientifique
      The Bethe–Born theory is applied to estimate the effective charges experienced by the ejected electrons at single, double and triple ionization of neon by fast electrons. The expansion coefficients appearing in the asymptotic expressions for total cross sections σn+ ~ [an+ln(Ei/In+) + bn+]/Ei are determined by fitting to these expressions the experimental data for single and multiple ionization of ...

    • Velocity-map imaging at low extraction fieldsPeer reviewedClosed access 

      2012, LECOINTRE, Julien; Horke, D. A.; Roberts, G. M.; Verlet, J. R. R., HENALLUX
      Article scientifique
      We present a velocity-map imaging (VMI) setup for photoelectron imaging that utilizes low electric extraction fields. This avoids any complications that could arise from electrostatic interactions between the extraction field and the molecular properties that are probed and has a minimal effect on the trajectory of ions in ion beam experiments. By using an attractive potential supplied to the detector, ...

    • Electron-impact dissociation of HeH+: absolute cross sections for the production of Heq+ (q = 1–2) fragmentsPeer reviewedClosed access 

      2014, LECOINTRE, Julien; Jureta, J. J.; Urbain, X.; Defrance, P., HENALLUX
      Article scientifique
      Absolute cross sections have been measured for electron-impact dissociative excitation and ionization of the helium-hydride ion (HeH+) leading to the formation of helium ions Heq+ (q = 1–2). Measurements have been performed for electron energies ranging from the respective thresholds up to 2.5 keV. For He+ production, the maximum absolute cross section for dissociative excitation is found to be (2.5 ...

    • Electron impact dissociation of ND+: formation of D+Peer reviewedOpen access 

      2011, LECOINTRE, Julien, HENALLUX
      Article scientifique
      Nitrogen is a common contaminant species in fusion reactors such as the ITER (International Thermonuclear Experimental Reactor). Thus, the collisional properties of nitrogen-containing plasma compounds arewidely studiedexperimentally andtheoretically. Here we show the results of absolute cross section measurements for the electron impact dissociative excitation of ND+ yielding D+, especially ...

    • Mass Spectrometric Investigation of Anions Formed upon Free Electron Attachment to Nucleobase Molecules and Clusters Embedded in Superfluid Helium DropletsPeer reviewedClosed access 

      2006, LECOINTRE, Julien; Denifl, S.; Zappa, F.; Mähr, I.; Probst, M.; Märk, T. D.; Scheier, P., HENALLUX
      Article scientifique
      Here we report the first mass spectrometric study of negative ions formed via free electron attachment (EA) to nucleobases (NBs) embedded in helium clusters. Pure and mixed clusters of adenine and thymine have been formed by pickup of isolated NB molecules by cold helium droplets. In contrast to EA of isolated molecules in the gas phase we observe a long-lived parent anion NB− and, in addition, ...

    • Electron-impact ionization of atomic hydrogen: dynamical variational treatmentPeer reviewedClosed access 

      2011, LECOINTRE, Julien; Defrance, P.; Kereselidze, T.; Machavariani, Z.S., HENALLUX
      Article scientifique
      A simple and straightforward calculating scheme is proposed for electron-impact single and multiple ionization of atoms. The method is based on the application of the Hulthén-Kohn dynamical variational principle. An effective charge seen by the scattered electron is determined for a certain type of trial wave functions mathematically in a rigorous way excluding any empirical assumptions. Validity ...

    • Energy distributions of H+ fragments ejected by fast proton and electron projectiles in collision with H2O moleculesPeer reviewedClosed access 

      2009, LECOINTRE, Julien; de Barros, A. L. F.; Luna, H.; Shah, M. B.; Montenegro, E. C., HENALLUX
      Article scientifique
      Experimental measurements of the kinetic energy distribution spectra of H + fragment ions released during radiolysis of water molecules in collision with 20, 50, and 100 keV proton projectiles and 35, 200, 400, and 1000 eV electron projectiles are reported using a pulsed beam and drift tube time-of-flight based velocity measuring technique. The spectra show that H + fragments carrying a ...

    • CRP on Atomic and Molecular Data for Plasma Modelling Volume 16Peer reviewedOpen access 

      2014, LECOINTRE, Julien, HENALLUX
      Article scientifique
      This publication, arising from a Coordinated Research Project on Atomic and Molecular Data for Plasma Modelling, provides information on new data relevant to the edge region of plasmas in nuclear fusion energy devices. In this region, molecules and molecular ions are formed and react with electrons and with each other and fusion plasma modelling requires cross-sections and rate coefficients for such ...

    • Absolute cross-sections and kinetic energy release distributions for electron-impact dissociation of D3+Peer reviewedClosed access 

      2009, LECOINTRE, Julien; Abdellahi El Ghazaly, M. O.; Jureta, J. J.; Belic, D. S.; Urbain, X.; Defrance, P., HENALLUX
      Article scientifique
      Absolute cross-sections for electron-impact dissociation of D+3 leading to the formation of D+ and D+2 products have been measured by applying the animated electron-ion beam method in the energy range from the respective thresholds up to 2.5 keV. The maximum total cross-sections are observed to be (13.9 ± 1.1) × 10−17 cm2 and (8.2 ± 0.1) × 10−17 cm2 (around 50 eV) for D+ and for D+2 fragments, ...

    • Isotope effects in electron-impact dissociation of D2H+Peer reviewedClosed access 

      2011, LECOINTRE, Julien; Jureta, J. J.; Defrance, P.; Urbain, X., HENALLUX
      Article scientifique
      Absolute cross sections have been measured using the crossed electron–ion beams method for electron-impact dissociation of the D2H+ molecular ion yielding H+, D+, HD+ and D+2 fragments. The collision energy ranges from a few eV up to 2.5 keV. Around the maximum, cross sections are found to be of a similar amplitude: (3.25 ± 0.08) × 10−17 cm2 for H+, (3.56 ± 0.15) × 10−17 cm2 for HD+ and (3.33 ± 0.11) ...

    • Rotational dependence of the dipole moment of 13CH3FPeer reviewedClosed access 

      2004, LECOINTRE, Julien; Cosleou, J.; Cacciani, P.; Herlemont, F.; Khelkhal, M; Pracna, P., HENALLUX
      Article scientifique
      When a gas sample of 13CH3F is prepared with a population of spin isomers far from the equilibrium given by nuclear spin statistics, it relaxes towards this equilibrium with an exponential decay rate. This rate is increased by submitting the molecules to a static electric field, emphasizing the role of the magnetic intramolecular interactions and of the collisions in the “quantum relaxation” process ...

    • Absolute cross sections and kinetic energy release for doubly and triply charged fragments produced by electron impact on CO+Peer reviewedClosed access 

      2006, LECOINTRE, Julien; Belic, D. S.; Jureta, J. J.; Becker, K.; Deutsch, H.; Limtrakul, J.; Märk, T. D.; Probst, M.; Defrance, P., HENALLUX
      Article scientifique
      Absolute cross sections for electron impact ionization of CO+ leading to the formation of doubly and triply charged products (CO2+, C2+ and O2+, C3+ and O3+) are reported in the energy range from their respective thresholds to 2500 eV. Around the maximum, cross section values are found to be (13.36 ± 0.56) × 10−18 cm2, (5.58 ± 0.55) × 10−18 cm2 and (1.37 ± 0.14) × 10−18 cm2 for CO2+, C2+ and O2+, ...

    • Electron impact multiple ionization of C+ and N+ and O+ ionsPeer reviewedOpen access 

      2014, LECOINTRE, Julien; Kouzakov, K. A.; Belic, D. S.; Defrance, P.; Popov, Y. V.; Shevelko, V. P., HENALLUX
      Article scientifique
      Absolute cross sections for electron impact single and multiple ionization of C+, N+ and O+ ions leading to the formation of Cq+ (q=2-4), Nq+ (q=2-5) and Oq+ (q=2-5) are reported in the energy range extending from the respective thresholds up to 2.5 keV. The general feature of the measured cross sections is investigated.

    • A crossed-beam experiment for electron impact ionization and dissociation of molecular ions: its application to CO+Peer reviewedClosed access 

      2006, LECOINTRE, Julien; Belic, D. S.; Cherkani-Hassani, H.; Jureta, J. J.; Defrance, P., HENALLUX
      Article scientifique
      A crossed electron–ion beam experimental set-up has been upgraded for the study of electron impact ionization and dissociation of molecular ions by means of ionic product detection. Both the experimental set-up and the data analysis procedures are described in detail for the estimation of (i) absolute cross sections, (ii) kinetic energy release distributions (KERD) and (iii) anisotropies of angular ...

    • Absolute cross sections and kinetic energy release distributions for electron-impact ionization and dissociation of CD+ 4Peer reviewedClosed access 

      2008, LECOINTRE, Julien; Belic, D. S.; Jureta, J. J.; Janev, R. K.; Defrance, P., HENALLUX
      Article scientifique
      Absolute cross sections for electron-impact dissociative excitation and ionization of CD+ 4 leading to formation of ionic products (CD2+ 4, CD+ 3, CD+ 2, CD+, C+, D+ 3, D+ 2, and D+) have been measured. The animated crossed-beams method is applied in the energy range from the reaction threshold up to 2.5 keV. Around 100 eV, the maximum cross sections are found to be (3.8±0.2) ×10-19 cm2, (10.8±1.5)× ...

    • Absolute cross-sections and kinetic-energy-release distributions for electron-impact ionization and dissociation of CD +3Peer reviewedClosed access 

      2009, LECOINTRE, Julien; Belic, D. S.; Jureta, J. J.; Janev, R. K.; Defrance, P., HENALLUX
      Article scientifique
      Absolute cross-sections have been measured for electron-impact dissociative excitation and ionization of CD+3/(CH+3) leading to formation of singly-charged fragments (CD +2, CH+, C+, H +2 and D+). The animated crossed-beams method is applied in the energy range from the reaction threshold up to 2.5 keV. The maximum cross-sections are found to be (14.0±1.0)×10-17 cm2, (6.5± 0.7)×10-17 cm2, (3.3± ...

    • Absolute cross-sections and kinetic-energy-release distributions for electron-impact ionization and dissociation of CD+ 2Peer reviewedClosed access 

      2009, Lecointre, J.; Belic, D. S.; Jureta, J. J.; Janev, R. K.; Defrance, P., HENALLUX
      Article scientifique
      Absolute cross-sections have been measured for electron-impact dissociative excitation and ionization of CD +2 leading to formation of CD 2+2, CD+, C+, D +2 and D+. The animated crossed-beams method is applied in the energy range from the reaction threshold up to 2.5 keV. The maximum total cross-sections are found to be (1.2±0.1)×10-17 cm2, (6.1±0.7)×10-17 cm2, (6.4±0.7)×10-17 cm2, (26.3±3.8)×10-19 ...