Perspectives for coherent optical formation of strontium molecules in their electronic ground state

Optical Feshbach resonances [ Phys. Rev. Lett. 94 193001 (2005)] and pump-dump photoassociation with short laser pulses [ Phys. Rev. A 73 033408 (2006)] have been proposed as means to coherently form stable ultracold-alkali-metal dimer molecules. In an optical Feshbach resonance, the intensity and possibly frequency of a cw laser are ramped up linearly followed by a sudden switch-off of the laser. This is applicable to tightly trapped atom pairs. In short-pulse photoassociation, the pump pulse forms a wave packet in an electronically excited state. The ensuing dynamics carries the wave packet to shorter internuclear distances where, after half a vibrational period, it can be deexcited to the electronic ground state by the dump pulse. Short-pulse photoassociation is suited for both shallow and tight traps. The applicability of these two means to produce ultracold molecules is investigated here for ⁸⁸Sr. Dipole-allowed transitions proceeding via the B ¹Σ_u⁺ excited state as well as transitions near the intercombination line are studied.