Author
D. S. Belic
Other affiliations: University of Belgrade
Bio: D. S. Belic is an academic researcher from Université catholique de Louvain. The author has contributed to research in topics: Electron ionization & Ionization. The author has an hindex of 9, co-authored 17 publications receiving 228 citations. Previous affiliations of D. S. Belic include University of Belgrade.
Papers
More filters
TL;DR: In this paper, the exact cross sections for electron impact ionization, dissociative excitation (DE), and dissociation ionization of N-2(+) ions are measured in the energy range from threshold to 2500 eV using animated crossed electron-ion beam method.
Abstract: Absolute cross sections for electron impact ionization, dissociative excitation (DE) and dissociative ionization of N-2(+) ions are measured in the energy range from threshold to 2500 eV. The animated crossed electron-ion beam method has been employed. The individual contributions of ionization products (N-2(2+)) and dissociation fragments (N+), which have both identical mass-to-charge ratio and average velocity, are deduced from the analysis of product velocity distributions. Particular attention was paid to determining the transmission efficiency for dissociation fragments, since their collection was incomplete during the measurements. Threshold energies and kinetic energy released to dissociation fragments are measured. The role of states contributing to different reactions is discussed. For DE, the present results are found to be much smaller than the results of Peterson et al (1998). For ionization (single and dissociative), a satisfactory agreement with their result is obtained as well as with the prediction of Kim et al (2000) obtained in the binary-encounter Bethe approximation.
40 citations
TL;DR: In this paper, 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.
Abstract: 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 distributions. Absolute cross sections are obtained separately for dissociative excitation ( DE) and for dissociative ionization ( DI). A double focusing magnetic field analyser is used for the observation of product velocity distributions, in the laboratory frame, at selected electron energies. The KERD in the centre of mass frame is calculated from the measured velocity distribution as well as the anisotropy of the angular distribution with respect to the initial orientation of the molecular ions. Results are reported for dissociative ionization and dissociative excitation of CO+ to C+ and O+ fragments in the energy range from about 5 eV to 2.5 keV. Absolute cross sections for DE at maximum, i. e. for an electron energy around 35 eV, are found to be ( 9.69 +/- 2.08) x 10(-17) cm(2) and ( 6.24 +/- 1.33) x 10(-17) cm(2), for C+ and O+, respectively, and the corresponding threshold energies are found to be ( 8.5 +/- 0.5) eV and ( 14.8 +/- 0.5) eV. The DE process leading to C+ production is seen to dominate at low electron energies. For DI, the absolute cross section is found to be ( 12.56 +/- 2.38) x 10(-17) cm(2) around 125 eV and the corresponding threshold energy is ( 27.7 +/- 0.5) eV. KERDs, which extend from 0 to 24 eV both for C+ and O+, exhibit very different shapes at low electron energy but similar ones above 100 eV, confirming the role observed respectively for DE and DI. The groups of states contributing to the different processes are identified by comparing present energies thresholds values and the KERDs with theoretical values. Anisotropies are estimated to be in the range 3-6% for both C+ and O+.
35 citations
TL;DR: In this article, the first absolute cross section measurements for double ionization of C+, N+, O+ and Ne+ ions by electron impact are reported, and the animated crossed beams method has been employed in the energy range from below ionization thresholds to approximately 2500 eV.
Abstract: The first absolute cross section measurements for double ionization of C+, N+, O+ and Ne+ ions by electron impact are reported. The animated crossed beams method has been employed in the energy range from below ionization thresholds to approximately 2500 eV. The classical binary encounter approximation overestimates measured cross sections by almost two orders of magnitude. Along the sequence, the cross section maximum does not follow classical scaling laws. A simple scaling law based on an electron pair ejection model is proposed for the prediction of direct double ionization. Inner-shell ionization followed by autoionization is seen to play a dominant role for C+ only.
30 citations
TL;DR: In this paper, the first absolute cross section measurements for single and double electron impact ionization of sodium-like Ar7+ are reported, and the animated crossed beams method has been employed in the energy range from threshold to 3000 eV.
Abstract: The first absolute cross section measurements for single and double electron impact ionization of sodium-like Ar7+ are reported. The animated crossed beams method has been employed in the energy range from threshold to 3000 eV. The measured cross sections for single ionization are higher than the theoretical and semi-empirical predictions by about 20-50%. This discrepancy has been associated with the contribution of the indirect ionization processes. The double ionization cross section is only 1% of the single one.
25 citations
TL;DR: In this article, the animated crossed beams method has been employed to measure cross sections for single ionisation of Li-like N4+, O5+ and Ne7+ by electron impact for energies from threshold to 2500 eV.
Abstract: Measured cross sections for single ionisation of Li-like N4+, O5+ and Ne7+ by electron impact are reported for energies from threshold to 2500 eV. The animated crossed beams method has been employed. In addition to direct ionisation, the 1s22s to 1s2l2l' excitation followed by autoionisation is shown to give a significant contribution to the total cross section, and its magnitude has been estimated for all three ions. Comparisons are made with other experimental results and different theoretical predictions. Cross sections for N4+ and O5+ are in a good agreement with previous results and the first result on Ne7+ ionisation is well reproduced by the Coulomb-Born calculations.
19 citations
Cited by
More filters
TL;DR: The R-matrix method is an embedding procedure which is based on the division of space into an inner region where the physics is complicated and an outer region for which greatly simplified equations can be solved.
372 citations
Book•
14 Apr 2008TL;DR: In this paper, the H2+molecule, Diatomic hydride ions, and the H3+ molecule have been studied using experimental methods and theoretical methods.
Abstract: 1 Introduction 2 Experimental methods 3 Theoretical methods 4 The H2+molecule 5 Diatomic hydride ions 6 Diatomic ions 7 The H3+ molecule 8 Polyatomic ions 9 Related processes 10 Applications
252 citations
TL;DR: The gas-phase chemistry in extraterrestrial space that is driven by reactions with atomic and molecular ions is reviewed, not only the observation, distribution and reactions of ions in space, but also laboratory-based experimental and theoretical methods for studying these ions.
Abstract: We review the gas-phase chemistry in extraterrestrial space that is driven by reactions with atomic and molecular ions. Ions are ubiquitous in space and are potentially responsible for the formation of increasingly complex interstellar molecules. Until recently, positively charged atoms and molecules were the only ions known in space; however, this situation has changed with the discovery of various molecular anions. This review covers not only the observation, distribution and reactions of ions in space, but also laboratory-based experimental and theoretical methods for studying these ions. Recent results from space-based instruments, such as those on the Cassini-Huygens space mission and the Herschel Space Observatory, are highlighted.
219 citations
TL;DR: A review of the knowledge of the structure, dynamics and collisions of atomic negative ions, as accumulated at the end of 2003, is given in this article, which describes how the research exploring these ions developed during the last decade.
215 citations
TL;DR: In this article, a wide range of oxygen-containing molecules following impact with electrons of carefully controlled energy is critically reviewed, ranging from diatomics, like O_2 and CO, to large molecules of biological and technological interest.
181 citations