Wave-Function Reconstruction for the Determination of the Scattering Length of Sr

We have investigated the photoassociation (PA) spectra of ultracold $^{88}$Sr atoms near the $5s^2 ^1S_0+5s5p ^1P_1$ atomic asymptote. The intensity modulation of the PA lines was used to reconstruct the ground-state scattering wave function, whose nodal point inferred the s-wave scattering length of $a=1.1(2)$ nm. The observed PA resonances also determined a precise lifetime of the $^1P_1$ state to be 5.263(4) ns.