Exciton localization in multichromophoric systems is often quantified with a participation number (or delocalization length): It is a scalar ranging from 1 (localization on one fragment) to 3 in our case (uniform delocalization over all three fragments). Eq. ( ) is, however, problematic in case S = 0 (or, equivalently, all F XY = 0), i.e., for purely doubly excited states. But, as we have seen (Fig. ), S = 0 is not the case for our system (for most of times, at least), and, in practice, even if F XY are small they are nonzero. Thus, PN can be calculated and it is shown in Fig. . Fitting the first picosecond of PN curves as