The product distribution of an antimony cracking effusion cell has been characterized using a time-of-flight mass spectrometer employing resonance-enhanced laser ionization. Source operating conditions have been identified under which predominately tetramers, dimers, and monomers of antimony are produced. Molecular beam epitaxy experiments employing the characterized antimony source for the growth of antimonide/arsenide superlattices and GaSb epilayers show that significant improvements in material quality can be obtained using monomeric antimony over that using molecular antimony species. A comparison of the surface chemistry of atomic and diatomic antimony species in the growth of several Sb-containing semiconductors will be presented.