The evolution of DELTAm=2 ground state coherences was investigated in
a thermal Rb atomic beam using spatially separated laser beams. The co
herence was created by optical pumping with a linearly polarized light
beam and was probed, after evolving in a homogeneous magnetic field v
ia the rotation of the plane of polarization of a second light beam. T
he observed signal shows dispersively shaped Ramsey fringes with a fri
nge width of 6 kHz.