Two-photon photoassociative spectroscopy of ultracold 88Sr

We present results from two-photon photoassociative spectroscopy of the least-bound vibrational level of the X (1)Sigma(+)(g) state of the Sr-88(2) dimer. Measurement of the binding energy allows us to determine the s-wave scattering length a(88)=-1.4(6)a(0). For the intermediate state, we use a bound level on the metastable S-1(0)-P-3(1) potential, which provides large Franck-Condon transition factors and narrow one-photon photoassociative lines that are advantageous for observing quantum-optical effects such as Autler-Townes resonance splittings.