Dipole-Dipole Interactions in a Cold Rydberg Gas

Richards, Brian, Physics - Graduate School of Arts and Sciences, University of Virginia
Jones, Robert, Department of Physics, University of Virginia

We investigate the strength and effects of dipole-dipole interactions in a cold Rydberg atom system. Our experiments explore the absence of collective decay due to dipole-dipole interactions, characterize dipole-dipole interactions and their dependence on Rydberg atom density and atomic motion, and explore possible methods to control atom separations using dipole-dipole interactions.

We study the decay of Rydberg atoms in a magneto-optical trap. The absence of collective decay or superradiant decay is attributed to variations in transition energies within the atom sample. These variations are dominated by inhomogeneities due to dipole-dipole exchange interactions for initial s states and by a combination of dipole-dipole and electric field inhomogeneities for initial p states.

We characterize the strength of the dipole-dipole resonant energy transfer reaction 32p32p to 32s33s by measuring population transfer to the 32s33s pair state as a function of electronic energy difference between the initial and final atom-pair states. We obtain resonance line shapes and widths that agree with a randomly distributed, nearest-neighbor model. We also use the line shapes to estimate the electric field inhomogeneity.

We explore two possible methods of controlling atom separation using dipole-dipole interactions. The first uses a chirped-frequency control laser to push closely separated atoms apart in a fully formed magneto-optical trap. The second uses a fixed-frequency control laser to prevent atoms from approaching past a minimum separation as the trap is formed. While atomic separation control was not observed in these measurements, we present several improvements for future experiments.

PHD (Doctor of Philosophy)
Rydberg Atoms, Dipole-dipole Interactions, Cold Gas
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