Coherent Optical Creation of a Single Molecule

We report coherent association of atoms into a single weakly bound NaCs molecule in an optical tweezer throughan opticalRamantransition. TheRaman technique uses a deeplybound electronic excited intermediate state to achieve a large transition dipole moment while reducing photon scattering. Starting fromtwo atoms in their relative motional ground state, we achieve an optical transfer efficiency of 69%. The molecules have a binding energy of 770.2 MHz at 8.83(2) G. This technique does not rely on Feshbach resonances or narrow excited-state lines and may allow a wide range of molecular species to be assembled atom by atom.