  We report the production of ultracold heteronuclear 7Li85Rb molecules in
excited electronic states by photoassociation (PA) of ultracold 7Li and 85Rb
atoms. PA is performed in a dual-species 7Li-85Rb magneto-optical trap (MOT)
and the PA resonances are detected using trap loss spectroscopy. We identify
several strong PA resonances below the Li (2s 2S1/2) + Rb (5p 2P3/2) asymptote
and experimentally determine the long range C6 dispersion coefficients. We find
a molecule formation rate (P_LiRb) of 3.5x10^7 s^-1 and a PA rate coefficient
(K_PA) of 1.3x10^-10 cm^3/s, the highest among heteronuclear bi-alkali
molecules. At large PA laser intensity, we observe the saturation of the PA
rate coefficient (K_PA) close to the theoretical value at the unitarity limit.
