Coherent Rydberg dynamics and interaction above room temperature: The frozen gas regime and beyond

The subject of this work is the experimental investigation of coherent Rydberg excitation and dynamics in a gas of alkali atoms above room temperature. By the use of a pulsed excitation scheme in ladder and four-wave mixing configuration, evidence for coherent evolution is observed on the nanosecond timescale inside and outside of the frozen gas regime. In the frozen gas regime, where all velocity classes follow the dynamics of non-moving atoms, evidence for interatomic Rydberg interaction is found. It is shown that the respective interaction strength can exceed the Doppler width, which is the prerequisite for strong correlations in a hot gas.