For other conjugated polymers, the two tuning procedures engender larger differences in excitation energies. Figure also presents data for a sequence of poly(pphenylenevinylene) n or (PPV) n oligomers, as well as poly(p-phenyl)nitroaniline [O 2 N-(C 6 H 4 ) n -NH 2 ], which we abbreviate as O 2 N(Ph) n NH 2 . For (PPV) n , the behavior is similar to that of the acenes in the sense that ω IE < ω GDD for a given oligomer size, although in this case ω IE seems to have converged by n = 7. There is a very slight upshift in ω IE for larger oligomers, which is mirrored in the HOMO/LUMO gaps; see Fig. for the latter. At first, we hypothesized that this might arise due to a slight twisting of the PPV chain in the optimized geometries that we employ, yet the same behavior is evident in coplanar geometries of (PPV) n . Furthermore, the uptick in ω IE has no effect on the S 1 transition energies, which are plotted in Fig. . We conclude that small fluctuations around the asymptotic value of ω IE reflect a degree of insensitivity to ω, in the vicinity of the optimally tuned value. Thus, the large-n behavior of ω IE reflects the limitations in computing the optimal value of ω when the objective function is rather flat.