Redistribution of atomic population among nearly degenerate Rydberg states through dipole-dipole interactions

Ultra-cold highly-excited atoms in a magneto-optical trap are strongly coupled by the dipole-dipole interaction. Rubidium atoms that have been excited to the 32d$_{5/2}$, $|m_{j}|$ = 1/2 sublevel can exchange energy when an applied static electric field tunes the Stark states into resonance. They do so via the densely packed set of resonant interactions 32d+32d$\rightarrow$34p+30g near 0.3 V/cm. Atoms that have exchanged energy and are now in the final p and manifold states can be coupled to a resonance involving 32d$_{5/2}$, $|m_{j}|$ = 3/2 and 1/2 states, which redistributes population among the $|m_{j}|$ sublevels. We present experimental and computational studies that investigate this redistribution.