Observation of Electric Quadrupole Transitions to Rydberg nd States of Ultracold Rubidium Atoms

Abstract

We report the observation of dipole-forbidden, but quadrupole-allowed, one-photon transitions to high Rydberg states in Rb. Using pulsed UV excitation of ultracold atoms in a magneto-optical trap, we excite $5s\to nd$ transitions over a range of principal quantum numbers $n=27-59$. Compared to dipole-allowed (E1) transitions from $5s\to np$, these E2 transitions are weaker by a factor of approximately 2000. We also report measurements of the anomalous $n{p}_{3/2}:n{p}_{1/2}$ fine-structure transition strength ratio for $n=28-75$. Both results are in agreement with theoretical predictions.

7 pages, 5 figures, 1 table