  We report the formation of ultracold $^{7}$Li$^{85}$Rb molecules in the
$a^{3}\Sigma^{+}$ electronic state by photoassociation (PA) and their detection
via resonantly enhanced multiphoton ionization (REMPI). With our dual-species
Li and Rb magneto-optical trap (MOT) apparatus, we detect PA resonances with
binding energies up to ~62 cm$^{-1}$ below the $^{7}$Li 2s $^{2}S_{1/2}$ $+$
$^{85}$Rb 5p $^{2}P_{1/2}$ asymptote. In addition, we use REMPI spectroscopy to
probe the $a^{3}\Sigma^{+}$ state and excited electronic $3^{3} \Pi$ and $4^{3}
\Sigma^{+}$ states, and identify $a^{3}\Sigma^{+} (v" = 7 - 13)$, $3^{3} \Pi
(v'_{\Pi} = 0 - 10)$ and $4^{3} \Sigma^{+} (v'_{\Sigma} = 0 - 5)$ vibrational
levels. Our line assignments agree well with ab initio calculations. These
preliminary spectroscopic studies on previously unobserved electronic states
are crucial to discovering transition pathways for transferring ultracold LiRb
molecules created via PA to deeply bound rovibrational levels of the electronic
ground state.
