The Frozen Core Approximation and Nuclear Screening Effects in Single Electron Capture Collisions

TL;DR

This paper compares two theoretical models for single electron capture in ion-atom collisions, showing that the active electron model aligns better with experiments and highlighting the importance of accurately modeling projectile-target interactions.

Contribution

The study introduces a detailed comparison between frozen core and active electron models for electron capture, emphasizing the significance of projectile-target Coulomb interaction modeling.

Findings

Active electron model agrees better with experimental data.

Frozen core approximation neglects electron state change without significant error.

Proper modeling of projectile-target Coulomb interaction is crucial.

Abstract

Fully Differential Cross Sections (FDCS) for single electron capture from helium by heavy ion impact are calculated using a frozen core 3-Body model and an active electron 4-Body model within the first Born approximation. FDCS are presented for H+, He2+, Li3+, and C6+ projectiles with velocities of 100 keV/amu, 1 MeV/amu, and 10 MeV/amu. In general, the FDCS from the two models are found to differ by about one order of magnitude with the active electron 4-Body model showing better agreement with experiment. Comparison of the models reveals two possible sources of the magnitude difference: the inactive electron's change of state and the projectile-target Coulomb interaction used in the different models. Detailed analysis indicates that the uncaptured electron's change of state can safely be neglected in the frozen core approximation, but that care must be used in modeling the projectile-target interaction.