  Graduate level physics curricula in many countries around the world, as well
as senior-level undergraduate ones in some major institutions, include
Classical Mechanics courses, mostly based on Goldstein's textbook masterpiece.
During the discussion of central force motion, however, the Kepler problem is
virtually the only serious application presented. In this paper, we present
another problem that is also soluble, namely the interaction of Schwinger's
dual-charged (dyon) particles. While the electromagnetic interaction of
magnetic monopoles and electric charges was studied in detail some 40 years
ago, we consider that a pedagogical discussion of it from an essentially
classical mechanics point of view is a useful contribution for students.
Following a path that generalizes Kepler's problem and Rutherford scattering,
we show that they exhibit remarkable properties such as stable non-planar
orbits, as well as rainbow and glory scattering, which are not present in the
ordinary scattering of two singly charged particles. Moreover, it can be
extended further to the relativistic case and to a semi-classical quantization,
which can also be included in the class discussion.
