Symmetry of dipositronium Ps2.

We work out the complete symmetry and spin problem for diatomic positronium Ps2 for the ground and singly excited states of zero orbital angular momentum. The general form of the wave function for each state is given, with due regard to charge conjugation parity. Annihilation rates are discussed, and correlations to dissociation products are deduced. We indicate how the approach is extensible to larger aggregates: i.e., PsPs(n), n>2.