Autler-Townes splitting in two-color photoassociation of ⁶Li

We report on high-resolution two-color photoassociation spectroscopy in the triplet system of magneto-optically trapped ⁶Li. Photoassociation is induced from the ground-state asymptote to the v=59 level of the excited 1³Σ_g⁺ state. This level is coupled to the v=9 level of the triplet ground state a³Σ_u⁺ by the light field of a Raman laser. The absolute transition frequencies are measured with an iodine frequency standard and the binding energy of the ground state is determined to be 24.391±0.020GHz. Strong coupling of the bound molecular states has been observed as Autler-Townes splitting in the photoassociation signal for different detunings of the Raman laser. From the splitting we determine the spontaneous bound-bound decay rate to be 4.3×10⁵s^-1 and estimate the molecule formation rate. The observed line shapes are in good agreement with the theoretical model.