  A simple two-atom model is shown to describe a Bose-Einstein condensate of
alkali atoms subjected to external magnetic field ramps near a Feshbach
resonance. The implications uncovered for two atoms in a trap can be applied at
least approximately to a many-atom condensate. A connection to observations is
accomplished by scaling the trap frequency to achieve a density comparable to
that of the experiments, which yields the fraction of atom pairs in the gas
that become molecules. A sudden approximation is used to model the external
magnetic field ramps in the vicinity of a two-body Feshbach resonance. The
results of this model are compared with recent experimental observations of
Donley et al. [1].
