[en] Ab initio self-consistent field molecular orbital calculations in an extended gaussian basis set plus configuration interaction calculations have been performed on the rectangular approach of two hydrogen molecules with fixed bond lengths to form square H4. Results for the ground and two low-lying excited electronic states are reported. One of these excited electronic states of H4 correlates with a ground state (X1Σsub(g)+) hydrogen molecule and a hydrogen molecule in its lowest singlet excited state (B1Σsub(u)+) at infinite intermolecular distance and, therefore, may be classified as an excimer state. (Auth.)