Spin and symmetry in low-energy electron energy-loss spectroscopy of transition metal oxides

The ratio of spin-hip to non-flip intensity in low-energy electron energy-loss spectroscopy for multiplicity-changing transitions within the 3d multiplet in NiO and CoO can be found exactly. It is shown to be independent of scattering geometry, incident energy and multiple scattering if well-defined local spins are assumed. For non multiplicity-changing transitions this ratio can be calculated approximately, using R-matrix techniques. The angular dependence of the scattering processes at low kinetic energies of the incident electron can be understood in terms of the point group symmetry at the target ion and the contribution of dominant angular momentum components to incoming and outgoing electron waves.