  We report on the collapse and revival of Ramsey fringe visibility when a
spatially dependent phase is imprinted in the coherences of a trapped ensemble
of two-level atoms. The phase is imprinted via the light shift from a Gaussian
laser beam which couples the dynamics of internal and external degrees of
freedom for the atoms in an echo spectroscopy sequence. The observed revivals
are directly linked to the oscillatory motion of atoms in the trap. An
understanding of the effect is important for quantum state engineering of
trapped atoms.
