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Electron impact ionization of thymine clusters embedded in superfluid helium droplets
2007,
- HENALLUX
,
- Article scientifique
Article scientifique
Embedding molecules in helium clusters has become a powerful technique for the preparation of cold targets for spectroscopy experiments, as well as for the assembly of complex, fragile molecular species. We have recently developed a helium cluster source and a pick-up cell to produce neutral beams of doped helium droplets, to be used as targets in studies on electron collisions with molecules of ...
Toward real-time charged-particle image reconstruction using polar onion-peeling
2009,
- HENALLUX
,
- Article scientifique
Article scientifique
A method to reconstruct full three-dimensional photofragment distributions from their two-dimensional (2D) projection onto a detection plane is presented, for processes in which the expanding Newton sphere has cylindrical symmetry around an axis parallel to the projection plane. The method is based on: (1) onion-peeling in polar coordinates [Zhao et al., Rev. Sci. Instrum. 73, 3044 (2002)] in which ...
Dissociative excitation of NeD+
2009,
- HENALLUX
,
- Article scientifique
Article scientifique
Measurements of NeD+ dissociative excitation cross section were obtained in Louvain-la-Neuve (UCL, Belgium) by using the animated crossed electron-ion beam method. The electronic structure of the system was calculated by using quantum chemistry calculations for the NeD+ ion and ab initio electron scattering calculations using the complex Kohn variational method for the resonant NeD neutral complex ...
Absolute cross sections and kinetic energy release distributions for electron-impact dissociative excitation and ionization of NeD+
2008,
- HENALLUX
,
- Article scientifique
Article scientifique
Absolute cross sections for electron impact dissociative excitation and ionization of NeD+ leading to the formation of singly and multiply charged products (D+, Ne+, Ne2+ and Ne3+) are reported, in the energy range from their respective thresholds to 2.5 keV. The animated crossed-beams method is used. For singly charged fragments, absolute cross sections are obtained separately for dissociative ...
Electron-impact ionization of singly-charged neon ions
2008,
- HENALLUX
,
- Article scientifique
Article scientifique
Absolute cross sections for electron-impact single and multiple ionization of Ne+ leading to the formation of Neq+ (q = 2–5) are reported. The animated crossed beams method is applied in the energy range from the respective thresholds up to 2.5 keV. The maximum cross sections are found to be (4.12 ± 0.21) × 10−17 cm2, (1.42 ± 0.07) × 1018 cm2, (2.57 ± 0.14) × 10−20 cm2, (8.78 ± 0.54) × 10−22 cm2 for ...
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 ...
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 ...
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, ...
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 ...