Efficient formation of strongly bound ultracold caesium molecules by photoassociation with tunnelling

We calculate the rates of formation and detection of ultracold Cs₂ molecules obtained from the photoassociation of ultracold atoms through the double-well 0_g^-(6S_1/2 + 6P_3/2) state. We concentrate on two features previously observed experimentally and attributed to tunnelling between the two wells (Vatasescu et al 2000 Phys. Rev. A 61 044701). We show that the molecules obtained are in strongly bound levels (v'' = 5, 6) of the metastable a³Σ_u⁺(6S_1/2 + 6S_1/2) ground electronic state.