  We have created and trapped a pure sample of 87Rb2 Feshbach molecules in a
three-dimensional optical lattice. Compared to previous experiments without a
lattice we find dramatic improvements such as long lifetimes of up to 700 ms
and a near unit efficiency for converting tightly confined atom pairs into
molecules. The lattice shields the trapped molecules from collisions and thus
overcomes the problem of inelastic decay by vibrational quenching. Furthermore,
we have developed a novel purification scheme that removes residual atoms,
resulting in a lattice in which individual sites are either empty or filled
with a single molecule in the vibrational ground state of the lattice.
