We report the use of photoassociative spectroscopy to determine the ground-state
s-wave scattering lengths for the main bosonic isotopes of strontium,
86Sr and
88Sr. Photoassociative transitions are driven with a laser red detuned by up to 1400 GHz from the $^{1}S_{0}\mathrm{\text{\ensuremath{-}}}^{1}P_{1}$ atomic resonance at 461 nm. A minimum in the transition amplitude for
86Sr at $\ensuremath{-}494\ifmmode\pm\else\textpm\fi{}5\text{ }\text{ }\mathrm{GHz}$ allows us to determine the scattering lengths
610a0<a86<2300a0 for
86Sr and a much smaller value of $\ensuremath{-}1{a}_{0}<{a}_{88}<13{a}_{0}$ for
88Sr.
Photoassociation spectroscopy experiments on
40Ca atoms close to the dissociation limit ${4s4s}^{1}{S}_{0}\ensuremath{-}{4s4p}^{1}{P}_{1}$ are presented. The vibronic spectrum was measured for detunings of the photoassociation laser ranging from 0.6 to 68 GHz with respect to the atomic resonance. In contrast to previous measurements, the rotational splitting of the vibrational lines was fully resolved. Full quantum-mechanical numerical simulations of the photoassociation spectrum were performed which allowed us to put constraints on the possible range of the calcium scattering length between
50a0 and
300a0.