  In this paper we analyze a two degree of freedom Hamiltonian system
constructed from two planar Morse potentials. The resulting potential energy
surface has two potential wells surrounded by an unbounded flat region
containing no critical points. In addition, the model has an index one saddle
between the potential wells. We study the dynamical mechanisms underlying
transport between the two potential wells, with emphasis on the role of the
flat region surrounding the wells. The model allows us to probe many of the
features of the roaming mechanism whose reaction dynamics are of current
interest in the chemistry community.
