Role of projectile electrons for target-recoil-charge-state production in intermediate-energy B2+-Ne collisions

Abstract

We apply an independent electron model to study q-fold target-charge-state production in 25-600 keV/nucleon B 2+-Ne collisions for which experimental and theoretical results were published recently [W. Wolff et al.,Phys. Rev. A 84, 042704 (2011)]. The model treats projectile and target electrons using a common potential and makes use of a single-determinant wave function for the combined system. The calculated total cross sections for positive recoil ion production as well as for Ne q+ production (q = 1,. .. ,4) determined in coincidence with an unchanged projectile charge state agree well with experiment where available, i.e., in the 30-400 keV/nucleon energy range. At energies below 200 keV/nucleon the projectile electrons are shown to play a crucial role in reproducing the experimental data for q = 1,. .. ,4. For the q 2 channels the inclusion of projectile electron contributions is needed even at energies above 200 keV/nucleon in order to reproduce the experimental data. As expected, the predictions for the q = 5 recoil charge state overestimate the experimental data due to a failure of the independent electron model for this extreme channel.

Multiple ionization of argon by helium ions

“…We calculate the multiple ionization cross sections of Ar by He + , with frozen He + , no capture, no electron loss, only pure ionization of the Ar target [34]. This is different from Kirchner proposal [12] that considers all the electrons active.…”

“…The present CDW-EIS results agree with DuBois data [20] for the single and double ionization cross sections, but overestimates the triple and higher multiple ionization. One of the reasons for this disagreement at intermediates energies could be the neglect of electron-electron correlation and of the capture contribution [12,47].…”

“…We remark again that in our calculations, the He + electron plays a role of screening the ion nucleus and it is not active in the collision (no capture and loss processes have been included). For heavier ions the inclusion of the capture channel within the multiple ionization calculations is important, even when the final ion charge remains unchanged as shown in [12] in comparison with B +2 in Ne experiments [9].…”

“…Another example within the IPM is the basis generator method (BGM) by Kirchner and coworkers [1,[10][11][12][13] applied to multiple ionization of Ne and Ar targets by bare and dressed ions. Recently this group [1,12,13] improved the theoretical description of the ionization by dressed ions by considering the two center electrons (projectile and target), and a time dependent interaction potential to include the changes in the target potential due to the subsequent loss of bound electrons. As expected, the changes (response) in the target potential weaken the multiple ionization, and lower cross sections are obtained.…”

“…On the other hand, the inclusion of transfer and ionization processes (that leaves the projectile in the same final charge state) also decreases the cross sections at intermediate energies. This contribution produced a clear difference in the triple and quadruple ionization of Ne by multicharged heavy ions such as B +2 [12].…”