A simple model for the scattering of electrons by a rotating dipole

The coupled equations describing the interaction of one electron with a dipole and hard sphere are shown to be exactly soluble, even when the energy levels of the dipole are taken into account. This model is used to discuss the critical moment for binding the electron in the dipole field. The condition for the existence of Feshbach resonances is similarly discussed. When the model is applied to calculate scattering phase shifts, shape resonances are found.