  We consider the quantum evolution of a pair of interacting atoms in a three
dimensional isotropic trap where the interaction strength is quenched from one
value to another. Using exact solutions of the static problem we are able to
evaluate time-dependent observables such as the overlap between initial and
final states and the expectation value of the separation between the two atoms.
In the case where the interaction is quenched from the non-interacting regime
to the strongly interacting regime, or vice versa, we are able to obtain
analytic results. Examining the overlap between the initial and final states we
show that when the interaction is quenched from the non-interacting to strongly
interacting regimes the early time dependence dynamics are consistent with
theoretical work in the single impurity many-body limit. When the system is
quenched from the strongly to non-interacting regime we predict large
oscillations in the separation between the two atoms, which arises from a
logarithmic divergence due to the zero-range nature of the interaction
potential.
