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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, ...
Electron-impact ionization of atomic hydrogen: dynamical variational treatment
2011,
- HENALLUX
,
- Article scientifique
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 molecules
2009,
- HENALLUX
,
- Article scientifique
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 ...