Light-shift-induced spin echoes in aJ=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 ${}_{}{}^2{}_{}{}^{}$ ${\mathit{S}}_{1/2}$ sodium ground state are in good qualitative agreement with theoretical predictions.