HENALLUX: Recent submissions
Voici les éléments 81-100 de 208
-
Electron impact dissociation of ND+: formation of D+
2011, HENALLUXArticle scientifiqueAbsolute cross sections for electron impact dissociation of ND+ leading to the formation of D+ have been measured by applying the animated electron-ion beam method in the energy range from the reaction threshold up to 2.5 keV. The maximum inclusive cross section is observed to be (16.8 ± 0.8) × 10−17 cm2 at the electron energy of 65.1 eV. The appearance energy for the D+ production is measured to ... -
Multiple ionization of C+, N+ and O+ ions by fast electron impact
2013, HENALLUXArticle scientifiqueAbsolute 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. The animated crossed beam method is applied in the energy range extending from the respective thresholds up to 2.5 keV. The concerned target ions belong to the second row of the periodic table, with configurations ... -
Water Fragmentation and Energy Loss by Carbon Ions at the Distal Region of the Bragg Peak
2007, HENALLUXArticle scientifiqueTime-of-flight mass spectrometry was used to investigate fragmentation and energy transfer processes in water by C ions at the distal part of the Bragg peak. Measurements of the positive ion fragments from ionization, electron capture, electron loss, transfer-loss and loss-ionization channels have allowed us for the first time (a) to obtain a quantitative determination of the energy lost by C ions ... -
Water-molecule dissociation by proton and hydrogen impact
2007, HENALLUXArticle scientifiqueTime-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 + ions
2011, HENALLUXArticle scientifiqueWe 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 Distributions
2010, HENALLUXArticle scientifiqueTime-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 electrons
2008, HENALLUXArticle scientifiqueThe 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 fields
2012, HENALLUXArticle scientifiqueWe 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) fragments
2014, HENALLUXArticle scientifiqueAbsolute 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+
2011, HENALLUXArticle scientifiqueNitrogen 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 Droplets
2006, HENALLUXArticle scientifiqueHere 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 treatment
2011, HENALLUXArticle scientifiqueA 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 molecules
2009, HENALLUXArticle scientifiqueExperimental 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 16
2014, HENALLUXArticle scientifiqueThis 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+
2009, HENALLUXArticle scientifiqueAbsolute 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+
2011, HENALLUXArticle scientifiqueAbsolute 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 13CH3F
2004, HENALLUXArticle scientifiqueWhen 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+
2006, HENALLUXArticle scientifiqueAbsolute 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+ ions
2014, HENALLUXArticle scientifiqueAbsolute 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+
2006, HENALLUXArticle scientifiqueA 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 ...