Light-Shift Induced Spin Echoes in a J=1/2 Atomic Ground State

We report on a spin-echo phenomenon that is induced between Zeeman sublevels by two laser pulses close to an optical resonance. The echo formation is due to a Zeeman light shift during the second off-resonant pulse; this light pulse creates a fictitious magnetic field that leads to the phase reversal of the spins. Our experimental results on the 2S1/2 sodium ground state are in good qualitative agreement with theoretical predictions