Peak shifting in absorption spectra when simulating time-dependent electron dynamics is a violation of the resonance condition. We physically expect that peaks in the spectrum will have changes in intensity as the population evolves, but that the energy of the peaks will remain constant rather than shifting in energy. The unphysical peak shifting phenomenon has been observed when using real-time TDDFT methods with the adiabatic approximation as the density is perturbed far from the reference ground state. To determine if there are sizedependent trends in peak shifting, the chosen molecules are driven from their initial ground states using frequencies resonant with S 0 → S 1 transition energies calculated from LR-TDHF as described in the previous section, resulting in single occupation of the HOMO and LUMO. The system is then propagated with the field off for 40 fs, and the resulting field-off dipole moment is Fouriertransformed to produce the absorption spectrum for each system.