On the convergence of the two-centre AO close-coupling method in ion - atom collisions

Abstract

Convergence of the two-centre atomic orbital (TCAO) close-coupling method in ion - atom collisions is carefully examined within the semiclassical impact parameter approximation. Calculations were carried out for protons colliding with H(1s) in the impact energy range 15 - 1000 keV. It is shown that the spurious oscillatory structures in previous large scale TCAO close-coupling calculations are due to the simultaneous use of the short-ranged pseudo-continuum states on both collision centres. By including a large number of pseudo-continuum states only at one centre in the TCAO expansion, we demonstrate that the resulting cross sections for excitation, capture and ionization for p + H(1s) collisions vary smoothly with collision energy and are in better agreement with the experimental data.

Dynamic instabilities in the interaction of transverse modes in a class-B laser

“…Here we have used the AOCC with the pseudostates method of Kuang and Lin [10,11] and note that this and other AOCC methods have typically been applied for light, fully stripped ions to treat capture up to about n = 4 or 5. For example, the Gaussian AOCC method of Toshima [20,21] has been applied to compute an extensive set of state-selective charge transfer data for light, fully stripped ions [22].…”

“…We have therefore computed these results to enable subsequent analysis of this component of the recombination emission spectrum. Finally, these advances in computational power have also enabled us to provide the first test of these CTMC calculations using a quantum mechanical approach, the atomic orbital close coupling (AOCC) method of Kuang and Lin [10,11]. In particular, AOCC calculations with basis sets large enough to test CTMC up to large principal quantum numbers have required significant new computing resources.…”

Excitation of the n=2 levels of hydrogen by proton impact for hydrogen beam diagnostics

“…In this method, the time-dependent electronic wavefunction is expanded in terms of functions such as those of the atomic orbitals of the isolated target atom and projectile ion, or other functions such as Gaussians or Sturmians, that may span not only the bound states but also the continuum. We adopt the AOCC with pseudostates method of Kaung and Lin [4,5], an approach we have used recently to study excitation and charge transfer in H + + H(2s) collisions [6] and for charge transfer in He 2+ , Be 4+ + H [7,8], and H + + He + and He 2+ + Li 2+ [9] collisions, in comparison with results of other methods, the classical trajectory Monte Carlo and lattice, time-dependent Schrödinger equation methods.…”

Electron excitation of hydrogen atom by ions impact in the energy range 20–1000 keV/amu

“…2CAO technique is most successful in providing accurate excitation cross sections. Following Slim and Ermolaev [11], Kuang and Lin [12], Toshima [13], thoroughly studied the convergence of excitation for the prototype reaction p+H(1s). Schultz et al [14] calculated the excitation cross section in H + and H collisions in a wide range of collision energies by lattice (equal space mesh) time-dependent method and their results are in reasonable agreement with the available experiments.…”