Coherent Transfer of Photoassociated Molecules into the Rovibrational Ground State

We report on the direct conversion of laser-cooled K-41 and Rb-87 atoms into ultracold (KRb)-K-41-Rb-87 molecules in the rovibrational ground state via photoassociation followed by stimulated Raman adiabatic passage. High-resolution spectroscopy based on the coherent transfer revealed the hyperfine structure of weakly bound molecules in an unexplored region. Our results show that a rovibrationally pure sample of ultracold ground-state molecules is achieved via the all-optical association of laser-cooled atoms, opening possibilities to coherently manipulate a wide variety of molecules.