Superradiance in ultracold Rydberg atoms

Experiments in dense, ultracold Rydberg atoms show a considerable decrease of excited state lifetimes compared to dilute gases. We show, using a novel formalism, that this behaviour can be modeled and explained as superradiance-type decay. In addition, we find that the tendency to decay into the highest-possible frequency channel is reversed as the density increases, and thus long-wavelength decay into the closest lying level is the most probable.