Spectroscopy of ultracold LiRb molecules

Using resonantly enhanced multiphoton ionization (REMPI), we detect ultracold LiRb molecules created via photoassociation (PA) in a $^7$Li/$^{85}$Rb dual species MOT. PA resonances below the D$_1$ and D$_2$ lines of Rb have been observed through both trap loss and REMPI spectroscopy. Decay pathways from different PA resonances allow us to map several different electronic potentials. To study the a$^3\Sigma^+$ potential, we create molecules in the $2(0^-)$ potential. These molecules mainly decay to the triplet electronic ground state. REMPI spectra show the vibrational levels of the a$^3\Sigma^+$ potential, as well as deeply bound levels belonging to the (3)$^3\Pi$ state through which the molecules are ionized. The vibrational structure of the X$^1\Sigma^+$ potential is observed via PA to other electronic potentials, such as the 4(1) which corresponds to the B$^1\Pi$ at close range. Molecules in the X$^1\Sigma^+$ state are likely ionized via the (4)$^1\Sigma^+$ electronic potential. Continuing these studies will help identify possible pathways from free atoms to LiRb molecules in the rovibronic ground state.