Stark effects on the phosphorescence origins of benzophenone and three derivatives (4,4′-dibromobenzophenone, 2-benzoylpyridine, and 3-benzoylpyridine) in a single 4,4′-dibromodiphenylether host crystal have been observed using electric field modulation spectroscopy. The magnitude of the effect for each molecule is determined by the vector difference in the dipole moments of the excited state and the ground state. These differences are found to be similar for all four molecules. This result demonstrates that the orbital configuration of the lowest triplet state is the same for each of these compounds and may indicate that the charge redistribution upon excitation is localized on the carbonyl group.