Detachment of electrons during the collision of two negative ions

The cross sections of the detachment of one and two electrons during the collision of two negative ions H- + H-, H- + Cs-, and Cs- + Cs- are calculated in a wide range of collision energies: from the energy threshold to approximately 100 keV. In adiabatically slow collisions, the detachment of electrons occurs as a result of one- or two- electron Auger decays whose rates are calculated in the approximation of asymptotically large separations between ions. For high collision energies, the cross sections of the electron detachment are calculated by the method of close coupling of states. The calculated cross sections are in good agreement with the results of experimental measurements made for the H- + H- collision. (C) 2001 MAIK "Nauka/ Interperiodica"

Summation rules for Coulomb wavefunction products

Sums of products of the Coulomb wavefunctions over degenerate manifolds have been obtained in a closed form. These sums appear in many atomic and molecular problems, The sums have been obtained making use of the properties of the Coulomb Green function G ((r) over right arrow, (r) over right arrow', E) in the limit E --> E-n where E-n is the eigenenergy of the hydrogen-like atomic ion. This paper develops the method described in our previous paper

New summation rules for Coulomb wave functions

Sums of products of the Coulomb wave functions over degenerate manifolds have been obtained in a closed form. These sums appear in many atomic and molecular problems. The sums have been obtained making use of the properties of the Coulomb Green's function G(r, r', E), in the limit E --> E-n, where E-n, is the eigenenergy of the hydrogenlike atomic ion. The closed Hostler-Pratt form of G in the coordinate representation has been used. The sums calculated are a consequence of the n degeneracy of the Coulomb atomic energy levels. This itself, as is well known, follows from the four-dimensional symmetry of the Coulomb problem for the hydrogen atom

Transfer Ionization in He-2+-h- Collisions - Cross-section Measurements in the Energy-range 0.2-1300 Ev

This paper reports on measurements of the cross section for transfer ionization in He2+-H- collisions over the barycentric energy range 0.16-1300 eV. The experimental method involves merged beams and coincident detection of the reaction products. The dependence of the cross section on the energy is rather similar to that of the one-electron exchange, suggesting that a two-step mechanism dominates the process

Electron impact double ionization of krypton ions (q=14-17)

Absolute cross sections for electron impact double ionization of krypton ions Krq+ (q = 14-17) have been measured from threshold to 5 keV. The animated crossed beam method has been employed. Direct double ionization is seen to reduce strongly along the isonuclear sequence. Ionization-autoionization from the inner L-shell is seen to be the dominant process. It is roughly approximated by the semi-empirical Lotz formula assuming total autoionization of the ionic intermediate states. Resonant capture and excitation processes implying the L-shell are also obtained for charge states 14-16

Electron-impact single ionization of krypton ions (q=12-18)

Absolute cross sections for electron-impact single ionization of krypton ions Krq+ (q = 12-18) have been measured. The animated crossed-beam method has been applied. The measurements cover the energy range from threshold to about 5.5 keV. The presence of ions formed in metastable states is observed for Kr18+, Kr16+ and Kr14+. Inner-shell excitation from the 2s, 2p, 3s and 3p subshells followed by autoionization is seen to play a dominant role for this reaction over the whole energy range. The importance of these excitation-autoionization processes explains the large underestimation of cross sections from the available theoretical and semi-empirical estimations which include direct processes only

Electron-impact dissociation of N2D+ cations to D+ fragments

Absolute cross sections for electron-impact dissociation of N2D+ cations to the light D+ fragments are reported for the first time. The animated electron-ion crossed-beam method is applied in the energy range from thresholds up to 2 keV. The heavy N+2 fragments are also detected and their kinetic energy distribution is analyzed at a selected electron energy. The measured cross-sections are corrected for incomplete collection of the light D+ fragments by performing careful analyser magnetic field scan together with a Monte-Carlo procedure. Inclusive absolute cross sections are determined. Dissociative excitation (DE) and dissociative ionization (DI) contributions are separated and the corresponding partial cross sections for D+ fragment production are determined at selected electron energies. The inclusive cross section for D+ fragment production has a maximum of (87±7)x10−18 cm2, at 95.1 eV, with the dominant contribution from the DI process

Electron impact ionization of argon ions (q=4-11)

Absolute cross sections for electron impact ionization of multiply charged argon ions (Arq+) have been measured in an animated crossed electron-ion beam experiment. Results are reported for single ionization (SI) (q = 4-6, 8, 10 and 11) ions and for double ionization (DI) (q = 5-11). The measurements cover the energy range from threshold to about 6000 eV The direct process is seen to dominate SI for q = 8, 10 and 11. For charge states 4-6, excitation-autoionization processes are seen to largely contribute to the ionization signal. In addition, metastable states are unambiguously identified for Ar5+ and Ar6+. Ionization-autoionization (IA) from the L shell accounts predominantly for DI of Arq+ (q = 5, 6). For charge states 7-11 direct DI is found to decrease strongly with respect to IA from the K shell