Direct production of ultracold rovibronic ground state LiRb molecules through photoassociation and spontaneous decay

We report a newly observed photoassociation resonance in $^7$Li-$^{85}$Rb, a mixed $2(1) - 4(1)$ excited state, that spontaneously decays to the rovibronic ground state. This resonance between ultracold Li and Rb is the strongest ground state molecule-forming photoassociation line observed in LiRb, and forms deeply bound $X \: ^1\Sigma^+$ molecules in large numbers. The production rate of the $v=0$ vibrational state is $\sim 4 \times 10^{3}$ molecules/s.