Theoretical triple differential cross section of the helium atom ionization with excitation to then=2 ion state

Abstract

The {e,2e) triple di8'erential cross section and generalized oscillator strengths of the helium atom ionization with simultaneous excitation have been calculated for the kinematic arrangements of the recent measurements and calculations of Dupre et al. [J.Phys. B 25, 259 (1992)]. The first Born calculation has been performed with an initial correlated multiconfiguration Hartree-Fock helium atom ground state and a coupled-channel final state of the ion and ejected "slow" electron. We find generally good agreement with the experiment, which is a substantial improvement on the previous calculations.PACS number(s): 31.20.Tz, 34.80.Dp

Second-order effects in (e, 2e) excitation-ionization of helium to (n= 2)

“…These have achieved various degrees of success in comparison with the experimental data but certainly give no overall accord. However, only this work and that of Mota-Furtado and O'Mahony (Mota-Furtado and O'Mahony 1989, O'Mahony and Mota-Furtado 1990, Kheifets et al (1994) and Knyr et al (1996) satisfy the minimal criterion implied in section 2.1, following equation ( 19), that ψ f should explicitly contain the couplings between the 1s, 2s and 2p states of He + . Thus Mota-Furtado and O'Mahony have used a 1s-2s-2p coupled eigenstate expansion for ψ f and also a 1s-2s-2p-3p-3d expansion where 3p and 3d are pseudostates.…”

“…There have been several theoretical studies of (e, 2e) excitation-ionization to He + (n = 2). Mostly these have been first Born calculations (Mota-Furtado and O'Mahony 1989, Langlois et al 1989, O'Mahony and Mota-Furtado 1990, Robaux et al 1991, Tweed et al 1993, Kheifets et al 1994, Knyr et al 1996, Nath et al 1996 or modified first Born approximations (Robaux et al 1992, Tweed et al 1993. None of these calculations are in convincing overall agreement with the data from Rome and Paris.…”

Convergent calculations for simultaneous electron-impact ionization-excitation of helium

“…With these choices we obtain essentially gauge-independent results. The present CCC formalism is similar to the coupled-channel optical (CCO) formalism employed previously by Kheifets et al (1994). However, in the present work we significantly improved the accuracy of the helium atom ground state and also implemented the CCC expansion for the e − -He + system.…”

Simultaneous excitation-ionization of helium to the state

“…A second approach has been to ignore the emitted photon and to probe the dynamics of the process using the two outgoing electrons in (e, 2e) experiments (Stefani et al 1990, Murray and Read 1992. Theoretical predictions of (e, 2e) outcomes were published by Robaux et al (1991), Dupré et al (1992), Franz andAltick (1992, 1995), Kheifets et al (1994), Nath et al (1996) and .…”