A novel technique is described for high-resolution spectroscopy. The time evolution of a coherent superposition of atomic substates created by a short resonant laser pulse is monitored via changes in polarization of a delayed probe pulse due to stimulated emission. As a demonstration the method was applied to the Zeeman splitting of the $6{}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}$ state of ytterbium.

• Received 17 March 1978

DOI:https://doi.org/10.1103/PhysRevLett.40.1373