  An atom moving in a spatially periodic field experiences a temporary periodic
perturbation and undergoes a resonance transition between atomic internal
states when the transition frequency is equal to the atomic velocity divided by
the field period. We demonstrated that spin nutation was induced by this
resonant transition in a polarized rubidium (Rb) atomic beam passing through a
magnetic lattice. The lattice was produced by current flowing through an array
of parallel wires crossing the beam. This array structure, reminiscent of a
multiwire chamber for particle detection, allowed the Rb beam to pass through
the lattice at a variety of incident angles. The dephasing of spin nutation was
reduced by varying the incident angle.
