Formation of ultracold metastable RbCs molecules by short-range photoassociation

Abstract

Ultracold metastable RbCs molecules are observed in a double species magneto-optical trap through photoassociation near the Rb(5S_1/2) + Cs(6P_3/2) dissociation limit followed by radiative stabilization. The molecules are formed in their lowest triplet electronic state and are detected by resonance enhanced two-photon ionization through the previously unobserved (3)³Π ← a ³Σ⁺ band. The large rotational structure of the observed photoassociation lines is assigned to the lowest vibrational levels of the 0⁺ or 0⁻ excited states correlated to the Rb(5P_1/2) + Cs(6S_1/2) dissociation limit. This demonstrates the possibility of inducing direct photoassociation in heteronuclear alkali-metal molecules at a short internuclear distance, as pointed out earlier [J. Deiglmayr et al., Phys. Rev. Lett., 2008, 101, 13304].