We form ultracold ground-state Rb2 molecules by photoassociating pairs of atoms in a magneto-optical trap into the 0u+ state, which decays radiatively into high vibrational levels of the X 1Σg+ state. Sensitive and vibrationally state-selective detection is achieved by means of resonantly-enhanced two-photon ionization with a pulsed laser. Frequency scans of the detection laser reveal a long vibrational progression to a previously unobserved electronic excited state, which we identify as the 21Σu+ state. Most of its vibrational spectrum is in excellent agreement with predictions based on ab initio potentials, although the lowest vibrational levels exhibit strong perturbative mixing with the triplet 23Π u state. The detection method reported here, with minor variations, should be effective for the entire potential well of the X state. In this work no transitions are observed from vibrational levels above v ≤ 118, but this turns out to be a limitation not of the detection method but rather of the photoassociative formation scheme, due to re-excitation of the highest-v levels by the same photoassociation laser that produces them.
|Original language||English (US)|
|Journal||Journal of Physics B: Atomic, Molecular and Optical Physics|
|State||Published - Oct 14 2006|
All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics
- Condensed Matter Physics