  We present spectra of ultracold $^7$Li$^{85}$Rb molecules in their electronic
ground state formed by spontaneous decay of weakly bound photoassociated
molecules. Beginning with atoms in a dual species magneto-optical trap (MOT),
weakly bound molecules are formed in the 4(1) electronic state, which
corresponds to the B$^1\Pi$ state at short range. These molecules spontaneously
decay to the electronic ground state and we use resonantly enhanced multiphoton
ionization (REMPI) to determine the vibrational population distribution in the
electronic ground states after spontaneous emission. Many of the observed lines
from the spectra are consistent with transitions from the X$^1\Sigma^+$ ground
electronic state to either the B$^1\Pi$ or D$^1\Pi$ electronic states that have
been previously observed, with levels possibly as low as X$^1\Sigma^+$ $(v'' =
2)$ being populated. We do not observe decay to weakly bound vibrational levels
of the X$^1\Sigma^+$ or a$^3\Sigma^+$ electronic states in the spectra. We also
deduce a lower bound of 3900 cm$^{-1}$ for the dissociation energy of the
LiRb$^+$ molecular ion.
