We predict feasibility of the photoassociative formation of Sr2 molecules in arbitrary 
vibrational levels of the electronic ground state based on state-of-the-art ab initio 
calculations. Key is the strong spin-orbit interaction between the c³?u, A¹Su? and B¹Su? 
states. It creates not only an effective dipole moment allowing free-to-bound 
transitions near the 1S + 3P1 intercombination line but also facilitates bound-to-bound 
transitions via resonantly coupled excited state rovibrational levels to deeply bound 
rovibrational levels of the ground X¹Sg? potential, with v" as low as v"=6. The spin-
orbit interaction is responsible for both optical pathways. Therefore, those excited 
state levels that have the largest bound-to-bound transition moments to deeply bound 
ground state levels also exhibit a sufficient photoassociation probability, comparable 
to that of the lowest weakly bound excited state level previously observed by Zelevinsky
et al. Phys. Rev. Lett. 96, 203201 (2006). Our study paves the way for an efficient 
photoassociative production of Sr_2 molecules in ground state levels suitable for 
experiments testing the electron-to-proton mass ratio.