H(2s)formation inH+-H and H-H collisions (original) (raw)
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Electron-impact-excitation cross sections of hydrogenlike ions
Physical Review A, 1997
Convergent close-coupling ͑CCC͒ and Coulomb-Born with exchange and normalization ͑CBE͒ methods are used to study electron-impact excitation of hydrogenlike ions. The nl→nЈlЈ cross sections demonstrate ͑i͒ good agreement between the CCC and CBE results, ͑ii͒ a scaling over ion nuclear charge z, ͑iii͒ a domination of the dipole (lЈϭlϮ1) contributions in total n→nЈ cross sections, and ͑iv͒ significant effect of electron exchange in the energy range xϽ3 ͑here x is the ratio of the incident electron kinetic energy to the transition energy E n,n Ј ). For ions with zϾ5 the n→nЈ cross sections obtained in the CCC and CBE approximations agree with each other to better than 10% for any x. An accuracy of the cross sections scaling over z 4 depends on z: for zϭ6 -18 the scaling is accurate to better than 10% ͑quantitative analysis is done for nЈϽ7), for ions with zϽ6 the cross sections deviate from the z 4 scaling more significantly ͑at x about unity͒. The n→nЈ cross sections are presented by a formula which fits our CCC and CBE results with an accuracy to better than 10% ͑for transitions with nϽnЈϽ7 in ions with zϾ5). The new Gaunt factor G(x) suggested for the widely used Van Regemorter formula ͓Astrophys. J. 136, 906 ͑1962͔͒ makes this formula accurate to better than 50% in the xϾ3 range and to better than 20% in the xϾ100 range. It is shown that the semiempirical formula by Vainshtein, Sobelman, and Yukov ͓Electron-Impact Excitation Cross Sections of Atoms and Ions ͑Nauka, Moscow, 1973͔͒ provides an accuracy to better than 50% for any incident electron energy. For xϽ2 this formula is accurate to better than 30%. These accuracy assessments are based on a comparison with our CCC and CBE results.
Journal of Physics B: Atomic and Molecular Physics, 1999
Abstract. Using Born's approximation we have analysed the structure of the doubly differential cross section for electron loss from fast H-near the forward direction. We show that electrons ejected with velocities slightly smaller than the projectile, originate in collisions in which the 'diffuse'electron of H-scatters as a nearly-free electron and excites (ionises) the target. Electrons ejected with velocities close to that of the projectile come from three sources:(i) double-electron loss in which the final state is strongly influenced by the ...
Impact Ionization in the Proton-H-Atom System: I. Theory
Physical Review, 1969
In a series of papers, of which this is the first, the calculation of the total cross section oI(&) for the process H +H(ls) 2H (E')+e (e), for initial relative energies E&500 eV, is described and performed. Here E is the relative energy of the final protons. This paper (I) describes the theory used, and paper II describes the calculation and results for the electronic part of the problem (wave functions and transition matrix elements). Work is being completed on the trajectory integrals which form the last part of the calculation. OI(E) is a total cross section with respect to scattering angles, but is differential in the final electron energy. The principle upon which the calculation is based is the approximate separability of electron and heavy-particle dynamics for both initial and final states, due to the mass disparity. The theory is an extension of that developed earlier by Thorson for transitions to discrete states. A. INTRODUCTION We describe here the calculation of the total cross section ol(e) for the impact ionization process H++H(ls) 2H+(E')+ e (e) for initial relative energies E& 500 eV. We have calculated ol(e) for the entire significant range of electron ener. .. gies, with a resolution of better than 1 eV; the approximations made in the theory are such (Sec. C) that differential cross sections with respect to angle cannot be accurately obtained. (For the direct impact mechanism of which this system is the prototype we do not, of course, expect fine structure of the order of our resolution or less.) At c.m. energies below 500 eV, the collision of
Excitation cross sections in a collision between two ground-state hydrogen atoms
Journal of Physics B: Atomic, Molecular and Optical Physics, 2021
We present excitation cross sections in a collision between two ground state hydrogen atoms using a four-body classical trajectory Monte Carlo model. Calculations were performed for impact energies in the range between 1.0 keV and 100 keV where the cross sections are highly relevant to the interest of the fusion research. Besides the total excitation cross sections for target and projectile, we also present partial excitation cross sections into the 2s and 2p states of the target. The partial excitation cross sections are compared with the previously obtained theoretical and experimental results.
An evaluation of amplitude occurring in ionization of H by e+-impact
An efficient evaluation of the amplitude o f ionization o f hydrogen atom by e * impact is presented without any ambiguity. The final state is represented by the product o f three Coulomb functions satisfying the correct asymptotic condition. Results are reported for the double differential cross section at forward ejection angle as a function of ejection energy and compared with the available theoretical findings.
Journal of Physics B: Atomic, Molecular and Optical Physics, 2006
The excitation of atomic hydrogen from the ground state to each of the 3s, 3p and 3d states has been studied for incident electron energies from 16.5 to 54 eV. Measurements of total cross sections and differential excitation cross sections (DCSs) for scattered electron angles from 5 • to 150 • have been made using a variety of coincidence methods. Within the summed experimental uncertainties of about 10% at best from statistical sources and 25% from absolute calibration sources the values calculated using the propagating exterior complex scaling and convergent close-coupling methods show good agreement with observations. DCS calculations for all s, p, d and f final states with n 4 are also presented over this energy range and reveal a systematic trend with respect to increasing n, final-state angular momentum and incident energy.
Impact Excitations of Hydrogen Atoms in Collisions with Protons and Antiprotons
The direct impact excitations of ground-state hydrogen atoms by protons and antiprotons are investigated by using an impact parameter treatment. The calculations are performed within the solution of the coupled differential equations arising from the one-center atomic-orbital close-coupling approach as well as the impact parameter version of the first and second Born approximations. We have considered calculations that allow couplings to the í µí±=1–5 states (up to g sub-levels) of the target atom as well as others, which neglect the effect of all states other than the initial and final states of the target atom. The sensitivity of the cross sections to the charge of the projectile is studied. The calculated cross sections are compared with those obtained by previous theoretical and experimental results.