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Multiple ionization of C+, N+ and O+ ions by fast electron impact
2013,
- HENALLUX
,
- Article scientifique
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. 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,
- HENALLUX
,
- Article scientifique
Article scientifique
Time-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,
- HENALLUX
,
- Article scientifique
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 + ions
2011,
- HENALLUX
,
- Article scientifique
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 Distributions
2010,
- HENALLUX
,
- Article scientifique
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 electrons
2008,
- HENALLUX
,
- Article scientifique
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 fields
2012,
- HENALLUX
,
- Article scientifique
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) fragments
2014,
- HENALLUX
,
- Article scientifique
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+
2011,
- HENALLUX
,
- Article scientifique
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 Droplets
2006,
- HENALLUX
,
- Article scientifique
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, ...