Updated photoassociation spectroscopy and mass-scaling of bosonic strontium

We present an updated investigation into the mass-scaling behavior of photoassociation resonances relative to the $^3P_1$ state in bosonic strontium. A previous mass-scaling model [Borkowski \textit{et al.}, Phys.\ Rev.\ A \textbf{90}, 032713 (2014)] was able to incorporate a large number of photoassociation resonances for $^{88}$Sr, but at the time only a handful of resonances were known for $^{84}$Sr and $^{86}$Sr. In this work, we perform a more thorough measurement of $^{84}$Sr and $^{86}$Sr bound states, identifying multiple new resonances at deeper binding energies out to -5~GHz. We also identify several previously measured resonances that cannot be reproduced and provide alternative binding energies instead. With this improved spectrum, we develop a mass-scaled model that accurately reproduces the observed binding energies of $^{86}$Sr and $^{88}$Sr to within 1~MHz. In order to accurately reproduce the deeper bound states, our model includes a second $1_u$ channel to more faithfully reproduce the depth of the potential. In addition, the optical lengths of the $^{84}$Sr $0_u^+,\ \nu=-2$ to $\nu=-5$ states are measured and compared to numerical estimates to characterize their use as optical Feshbach resonances.