Coupling of molecular spin in electron-molecule scattering

Abstract

We consider spin-dependent effects in low-energy electron molecule scattering. Until now no explicit spin dependent effects have been included in ab initio calculations. We discuss the fine-structure effect, well known from atomic physics, for diatomic molecules as a model which can describe deviations from pure exchange scattering. Numerical results for the a3 Pi excitation of CO will give an indication of the magnitude of the effects. Resolving the fine-structure of the target leads to the different coupling schemes for diatomic molecules. We consider in this paper Hund`s cases (a) and (b) as the two most important ones. In particular, differential cross sections and spin polarization for unpolarized projectiles and targets are discussed. For molecules obeying Hund`s case (a) coupling scheme orientation and alignment parameters are introduced.