Multichannel tunneling in theCs20g−photoassociation spectrum

Two features with large rotational structure, observed at detunings ${\delta }_1=-2.14{\mathrm{cm}}^{-1},{\delta }_2=-6.15{\mathrm{cm}}^{-1}$ in the cesium photoassociation spectrum, are interpreted as due to the combined effect of tunneling through the barrier of the double-well $0_g^{-}{(6s+6p}_{3/2})$ potential, and channel mixing in the inner-well region. A precise value of the height of the barrier is given. The levels affected by these effects are expected to decay into low vibrational levels of the lowest triplet state, thus producing ultracold molecules.