Enhancement of the formation of ultracold ${}^{85}$Rb${}_2$ molecules due to resonant coupling

Abstract

We have studied the effect of resonant electronic state coupling on the formation of ultracold ground-state ${}^{85}$Rb${}_2$. Ultracold Rb${}_2$ molecules are formed by photoassociation (PA) to a coupled pair of $0_u^{+}$ states, $0_u^{+}(P_{1/2})$ and $0_u^{+}(P_{3/2})$, in the region below the $5S+5P_{1/2}$ limit. Subsequent radiative decay produces high vibrational levels of the ground state, $X^1{\Sigma }_g^{+}$. The population distribution of these $X$ state vibrational levels is monitored by resonance-enhanced two-photon ionization through the $2^1{\Sigma }_u^{+}$ state. We find that the populations of vibrational levels $v^{\prime \prime }$=112$-$116 are far larger than can be accounted for by the Franck-Condon factors for $0_u^{+}(P_{1/2})\to X^1{\Sigma }_g^{+}$ transitions with the $0_u^{+}(P_{1/2})$ state treated as a single channel. Further, the ground-state molecule population exhibits oscillatory behavior as the PA laser is tuned through a succession of $0_u^{+}$ state vibrational levels. Both of these effects are explained by a new calculation of transition amplitudes that includes the resonant character of the spin-orbit coupling of the two $0_u^{+}$ states. The resulting enhancement of more deeply bound ground-state molecule formation will be useful for future experiments on ultracold molecules.

6 pages, 5 figures; corrected author list

References in corpus (3)

• Quo vadis, cold molecules? - Editorial review
• Feshbach resonances in rubidium 87: Precision measurement and analysis
• Stabilization of Ultracold Molecules Using Optimal Control Theory

Cited by in corpus (1)

• Engineering an all-optical route to ultracold molecules in their vibronic ground state