In photosynthesis of purple bacteria, excitation energy of bacteriochlorophylls in the core antenna LH1 is transferred to the excited state (P*) of the special pair (P) in the reaction center (RC). Subsequently, charge separation to the adjacent monomeric bacteriochlorophyll (B) occurs from P*, producing P+B- as initial energy fixation in the RC. Although the absorption-peak energy of P is appreciably (by 200-430 cm(-1)) higher than that of the lowest excited state LH1* of LH1, these sequential events occur still at low temperatures for the energy trapping in Rhodobacter sphaeroides, while in Rhodopseudomonas viridis LH1* is unistep converted to P+B- in the RC by the superexchange mechanism due to quantum-mechanical virtual mediation by P* at low temperatures, as clarified in part I (Sumi, H. J. Phys. Chem. B 2002, 106, 13370). Such differences arise since in the free energy LH1* is slightly (by similar to50 cm(-1)) higher than P* in Rb. sphaeroides, while in Rps. viridis LH1* is still considerably (similar to150 cm(-1)) lower than P* in the free energy, after reorganization of the medium around P*. An experiment is proposed to investigate unifiedly such differences, by photoexcitation of a single RC from either Rb. sphaeroides or Rps. viridis. When the photon energy E is higher than about the free energy Eo for P*, the production rate of P+B-, measurable as the rate of absorption by the RC, will be nearly equal to that by P*, measurable as its excitation spectrum, at all temperatures by the sequential mechanism. When E is considerably lower than E-0, the former will become much larger than the latter at low temperatures by the superexchange mechanism. The photoinduced production rate of P+B- mediated by P* is given as an analytic formula bridging the two limits, for analyzing such observations expected.