Abstract. Rotationally resolved excitation of the a*Ag and blZgStates of 0 2 is considered. Results for the relevant state multipoles are given. The anisotropy produced by electron impact is visualised by figures of the angular distribution of the molecular axes in the excited states.

We consider the rotationally resolved excitation of heteronucleax diatomic molecules.Particular emphwis is on the selective population of the A-doublet states and their coherence propenies produced during the collision. The general theory is developed and the relevant selection rules are derived. Using recently obtained T-"ix elements for the a ' l l excitation of CO we have calculated the relevant parameters of interest for several energies as a function of the scattering angle. The results show that the 6 = + I members of the Adoublei states are pmferentially excited for small and large scattering angles. It is show'n thaf a considerable amount of coherence between the A-doublet stat= is produced which is responsible for a nonvanishing electric dipole moment induced by the collision.

We consider spin-dependent effects in low-energy elecvan molecule scattering. Until now no explicit spin dependent effects have been included in ob 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 mulls for the a 3 n excitation of CO will give an indication of the magnitude of the effects. Resolving the finestructure of h e tuget leads to h e 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 cf&e (a) coupling scheme orientation and alignment parameters are inuoduced.