Taking |T (r elec , r hole )| 2 seriously as the probability distribution for the exciton, this quantity should afford the correlated probability of finding the hole at position r hole given the presence of the excited electron at position r elec . A schematic view of |T (r elec , r hole )| 2 as a two-dimensional probability distribution is presented in Fig. . According to Eq. ( .3), this plot conveys the same qualitative information, in the same way, as does a heat-map plot of Ω (e.g., in Table ), but does so in real space whereas Ω A→B does so in atom or functional-group space. Either way, the diagonal direction in a plot of r elec versus r hole measures charge separation, with a characteristic length scale L coh [Eq. (4.24)]. The anti-diagonal direction measures the total size of the exciton, i.e., delocalization over atoms, and can be measured using PR adiag [Eq. (4.25)].