Single- and double-ionization processes using Gaussian-type orbitals: Benchmark on antiproton-helium collisions in the keV-energy range

Abstract

We present a simple and efficient method for computing single and double ionization cross sections in ion-atom and ion-molecule collisions using L 2 Gaussian basis sets. Gaussian functions are widely employed to compute bound states of ions, atoms and molecules. However, the description of continuum states, and therefore ionization phenomena, remains a theoretical challenge. Our approach is tested on the benchmark system antiproton-helium collisions in the so-called intermediate energy range. A good agreement with numerically exact calculations is observed. The proposed method is general and can thus be employed in any collisional systems in the challenging non-perturbative regime. Our work opens the way to investigate multiple ionization processes by ion impact in multi-center poly-electronic systems.

Study of single electron capture in O6+ + He collisions

“…In the present work, a two-active-electron SCASCC method [7][8][9][10][11][12] was used to investigate the collisions of O 6+ with He. Here introduce the main features of this method briefly.…”

“…The discrepancies with the experimental data had been observed for their partial charge transfer cross sections in the considered energy region. Recently, a two-active electrons close-coupling method has been developed by [7][8][9][10][11][12] which includes the fully correlation between two electrons. Moreover, many different competing reaction channels for the collision systems can be included as the same time.…”

Calculation of Energy Loss in Antiproton Collisions with Many-Electron Systems using Ehrenfest's Theorem

“…[9]. A recent study using interesting methodology that can be implemented for molecular targets on the one hand confirmed the double ionization cross sections for He targets [10], but also pointed out how difficult it is to get a handle on extracting accurate double ionization cross sections.…”

Summary Report of the Third Research Coordination Meeting on Data for Atomic Processes of Neutral Beams in Fusion Plasma

“…For intermediate energy range (~100 eV/u < E < ~100 keV/u) collisions，AOCC calculations have been performed for a large number of systems and charge transfer cross section have been obtained for Ne q+ -H (q = 6 -10) [7], Be 4+ -H (1s, 2s, 2p)[in preparation], C 4+ -He [8], Li 3+ -Li (1s 2 2s, 1s 2 2p) [9], He + -He(1s 2 ;1s2l 1,3 L) [10][11][12][13], H + -Be + [14], H + + H − [15], N 5+ -H2 [16], H + -Mg [17][18][19] etc., excitation cross sections have been obtained for Be 4+ -H (1s, 2s, 2p) [in preparation] and Be 3+ -Li [20], and ionization cross sections have been obtained for Be 4+ -H (1s, 2s, 2p) [in preparation] and antiproton -helium [21]. For high charged ions or excited state target, very large basis sets are needed to obtain convergent results; and for excitation and ionization processes, even larger basis sets are needed for convergence.…”