We report the engineering of molecular potentials at large interatomic
distances. The molecular states are generated by off-resonant optical coupling
to a highly excited, long-range Rydberg molecular potential. The coupling
produces a potential well in the low-lying molecular potential, which supports
a bound state. The depth of the potential well, and thus the binding energy of
the molecule, can be tuned by the coupling parameters. We characterize these
molecules and find good agreement with a theoretical model based on the
coupling of the two involved adiabatic potential energy curves. Our results
open numerous possibilities to create long-range molecules between ultracold
ground state atoms and to use them for ultracold chemistry and applications
such as Feshbach resonances, Efimov physics or the study of halo molecules