Semi-Classical Collision Formalism with Energy and Momentum Transfer
Résumé
As expected, the semi-classical theory of atom-electron and atom-ion collisions ( tealt{b11 Se62}; see also tealt{b11 SB96}) leads to incorrect results when it is applied to impact polarization computations. This is due to the fact that, near the threshold, the Δ M=± 1 transitions between Zeeman sublevels remain open, even though the momentum conservation law tep{b11 PS58} implies that they should be forbidden at the exact threshold. An approximate model of momentum transfer is proposed, which corrects this behavior, leading to a fairly good agreement with observed impact polarization for several target atoms. The agreement is improved also for the total cross-section, because the Δ M=± 1 cross-sections were previously overestimated. Comparison with experimental results are shown, for electron-atom impact polarization and total cross-section. As a second step, energy transfer is also taken into account, by splitting the collision process in two halves: the first half is modeled within the initial conditions, while the second half is modeled within the final conditions.