Observation of Dicke Superradiance in Optically Pumped HF Gas

We have found that room-temperature HF gas at millitorr pressures, optically pumped to produce a total inversion at a rotational transition in the $v=1\mathrm{}$ vibrational state, emits a superradiant pulse with ringing after a considerable delay (∼ microseconds). A semiclassical analysis shows that for a high-gain system the pulse evolution is determined by a single parameter ${\tau }_R$, and that inhomogeneous broadening is unimportant. Close agreement between theory and experiment is obtained.