where K defines specific orbital interactions between the donor (PC*) and the acceptor (substrate), J is the spectral overlap integral, RDA represent the donor-acceptor distance and L is the sum of the van der Waals radii of the donor and acceptor. A smaller ΔET (Equation ) will correlate with a greater degree of spectral overlap, and as a consequence, a faster kDET (Equation ). In addition, for the energy transfer to be exergonic, ΔET should be greater than zero. For the cases where ΔET < 0, the transition is endergonic. As spectral overlap remains a requirement of DET, the implication of ΔET < 0 is that the PC* must have vibrational or rotational states that are greater in energy than some of those of the acceptor in its electronic excited state in order for the DET to be thermodynamically feasible. To fully assess and understand the yields achieved by a particular PC in a photocatalytic reaction, the aforementioned optoelectronic parameters that govern PET or PEnT must be determined. For example, for PET an accurate measurement of both the ground and excited state redox potentials, the latter dependent on the excited-state (singlet or triplet, depending on the type of PC) optical gaps, are required. For PEnT, the ET of the PC should be evaluated.