  This paper deals with the conversion between atoms and molecules in optical
lattices. We show that in the absence of collisional interaction, the atomic
and molecular components in different lattice wells combine into states with
macroscopic condensate fractions, which can be observed as a strong diffraction
signal, if the particles are abruptly released from the lattice. The condensate
population, and the diffraction signal are governed not only by the mean number
of atoms or molecules in each well, but by the precise amplitudes on state
vector components with different numbers of particles. We discuss ways to
control these amplitudes and to maximize the condensate fraction in the
molecular formation process.
