Creation of Ultracold 87Rb 133Cs Molecules in the Rovibrational Ground State

We report the creation of a sample of over 1000 ultracold ⁸⁷Rb ¹³³Cs molecules in the lowest rovibrational ground state, from an atomic mixture of ⁸⁷Rb and ¹³³Cs, by magnetoassociation on an interspecies Feshbach resonance followed by stimulated Raman adiabatic passage (STIRAP). We measure the binding energy of the RbCs molecule to be h c ×3811.576 (1 ) cm^-1 and the |v^''=0 ,J^''=0 ⟩ to |v^''=0 ,J^''=2 ⟩ splitting to be h ×2940.09 (6 ) MHz . Stark spectroscopy of the rovibrational ground state yields an electric dipole moment of 1.225(3)(8) D, where the values in parentheses are the statistical and systematic uncertainties, respectively. We can access a space-fixed dipole moment of 0.355(2)(4) D, which is substantially higher than in previous work.