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"

Electron capture and excitation in slow H+ + He*(n) collisions

Electron capture and excitation (de-excitation) processes in slow collisions of protons with excited helium, H+ + He*(1s, NL) --> H*(nl) + He+(1s) or --> H+ + He*(1 s, N'L'), are studied by using the close coupling of the states {N, n} = 2, 3, 4 within the approach described in a previous paper. At small collision velocities, 10(6) cm s(-1) < v < 5 x 10(7) cm s(-1), the cross sections for excitation(de-excitation) are very large, due to the importance of two-step transitions. The coupling of the states with different principal quantum numbers significantly increases the cross sections for electron capture at adiabatically small collision velocities

Electron detachment of H- in collisions with multiply charged ions

Total cross-section calculations are reported for the electron detachment from H- in collision with multiply charged ions by using a simple two-state model. In the collision energy range where this model is expected to be realistic, results are in fair agreement with both very recent experimental and theoretical results

Sums of products of Coulomb wave function over degenerate states

The sums of products of Coulomb wave function over degenerate states are expressed in terms of quadratic forms that depend on the wave function of only one state with zero orbital angular momentum l = m = 0. These sums are encountered in many fields in the physics of atoms and molecules, for example, in investigations of the perturbation of degenerate atomic energy levels of a small potential well, a delta-function potential. The sums were found in an investigation of the limit of the Coulomb Green's function G(r, r', E), where the energy parameter E approaches an atomic energy level: E --> E-n, E-n = -Z(2)/2n(2). The Green's function found by L. Hostler and R. Pratt in 1963 was used. The result obtained is a consequence of the degeneracy of the Coulomb energy levels, which in turn is due to the four-dimensional symmetry of the Coulomb problem. (C) 2000 MAIK "Nauka/Interperiodica"

Electron capture and excitation in slow H++He*(n=3) collisions

The electron-capture and excitation processes in slow collisions of protons with He*(1s3l) are studied using the close-coupling method within the semiclassical approximation. The Stark splitting of electron-capture states on H is explicitly taken into account and the coupling-matrix elements between these states and the initial angular-momentum states on He are calculated analytically. The cross sections for excitation (de-excitation) and single-electron capture to specific spherical hydrogen states have been calculated in the relative velocity range 2 x 10(6)-1.3 x 10(8) cm s(-1). The cross section values for both types of processes in the considered velocity range are found to be large (10(-14)-10(-13) cm(2)) due to the large values of electron-exchange couplings at large internuclear distances. The excitation (de-excitation) processes are controlled by two-step exchange (capture and re-capture) transitions rather than by direct coupling among the states centred on He

Transfer ionization in slow H++H- collisions

The transfer ionization reaction H-a(-) + H-b(+) = H-a(+) + H-b(1s) + e, on which we had previously carried out experiments and calculations, is reconsidered here at higher collision energies and interpreted as ionization of weakly bound electron of the H- ion, accompanied by a simultaneous resonant exchange of the 1s core electron. The ionization of H- is treated as being strongly coupled to the dominant mutual neutralization channels H-a(-) + H-b(+) = H-a (1s) + H-b (nlm), and the cross sections for all relevant reaction channels are calculated by using the molecular-orbital close-coupling scheme