Doubly differential cross sections for K-shell ionization by electron and positron impact

We have investigated the universal scaling behaviour of the doubly differential cross sections for single K-shell ionization by electron and positron impact. The study is performed within the framework of non-relativistic perturbation theory, taking into account the one-photon exchange diagrams. The results obtained are valid for arbitrary atomic targets with moderate values of the nuclear charge Z. In the case of low-energy positron scattering, the doubly differential cross section exhibits prominent interference oscillations, which may serve as a focus for near-future experimental investigations.