Influence of Dipole-Dipole Interaction on Electron Dynamics in a Cold Rydberg Gas

Electron dynamics in dipole-dipole (DD) coupled Rydberg atoms show some unique properties that do not exist in individual atoms. The goal of the research in this dissertation is to reveal and control the electron dynamics influenced by DD interaction in cold Rydberg gases.

We have studied the decay of Rydberg excitations in a cold Rb gas and find no evidence for superradiance. The decay rates and population redistribution we observe are consistent with a model that considers only spontaneous emission from, and blackbody redistribution within, isolated atoms. Suppression of superradiant emission is likely due to variations in transition energies across the cold Rydberg atom sample. For initial s states, these variations are dominated by inhomogeneities in DD exchange interactions within the random ensemble. Such inhomogeneities will necessarily be present in any measurement involving a large number of atoms where the separation between atoms is not well defined. For initial p states, the suppression is likely due to a combination of DD exchange and electric field inhomogeneities.

We have also explored the evolution of Rydberg wavepackets in the presence of strong dipole-dipole interactions in a frozen gas. The distribution of atom separations results in an inhomogeneity in the strength of the exchange coupling between neighboring atoms, causing a dephasing of the macroscopic coherence.

We have also explored the mechanism of wavepacket coherence transfer from one Rydberg atom to a neighboring Rydberg atom via DD interactions utilizing the resonant DD coupling transition 25s33s↔24p34p. The phase-shift of the observed interference modulations in the 34p signal, relative to that in 25s, is a signature of wavepacket coherence transfer between atoms driven by electron correlations resulting from the controlled DD coupling between them.