Second-order Born model for two-electron atomic ionization by fast charged-particle impact

Abstract

We develop a theoretical model to describe simultaneous ionization excitation and double ionization of a two-electron atomic shell (i.e., He 1s 2 ) by a fast charged-particle impact. The model accounts for the projectile-target interaction to the second order whereas the interaction of the two target electrons ejected into continuum is treated nonperturbatively by the convergent close-coupling (CCC) method. In the second-order term, all intermediate states of the target between two subsequent interactions with the projectile are weighted equally with an average energy denominator (the so-called closure approximation) and only the dipole interaction of the projectile with the target is included. The model is suited to describe two-electron ionization processes with large projectile velocity, small momentum transfer, and small to intermediate energy of the ejected electrons. The model is applied to ionization excitation and double ionization of He by electron and positron impact in kinematics of recent experiments.

Convergent calculations of double ionization of helium: From(γ,2e)to(e,3eKheifets1, Bray2 2004Phys. Rev. ASelf Cite391230View full textAdd to dashboardCite

“…1 and 2, we show calculations with three groundstate wave functions: Pluvinage, Le Sech, and Hylleraas. In addition, the calculations were performed utilizing the first and second Born approximations [14] and found to be different by less then 10% (although not quantified, a similar conclusion was reached in Ref. [20]).…”

“…Following the implementation of the second Born term [14] we are able to test the contribution of this term for the kinematics considered here. We have also implemented the Pluvinage ground state and its improved version as prescribed by Le Sech and co-workers [15,16], who argued that the former lacked the screening of two-particle interactions by the third particle.…”

and differential cross sections for the double ionization of water molecule

“…Kheifets [11] has shown that the second Born approximation, which well describes the TS2 mechanism, is important at 0.5 keV and weak for higher incident energies, as shown by Rasch et al [12] and by El Mkhanter and Dal Cappello [13]. So we consider here only the SO and TS1 mechanisms and perform calculations for future (e, 3e) and (e, 3 − 1e) experiments by giving the best choices for the kinematical conditions.…”

Fivefold differential cross sections for electron-induced double ionization of outer and inner valence (1t2 and 2a1) molecular orbitals of CH4

“…The TS2 mechanism is then a second order process that can only be described within the 2nd Born approximation. However, up to now, only few models have been reported within the secondorder Born approximation, the major part of them being limited to simple atomic targets [39][40][41][42][43][44][45][46]. Considering the double ionization of molecular targets, to the best of our knowledge there are only two available models in the literature that use the 2nd Born approximation for describing the double ionization of H 2 [47,48].…”