The 161 and 176 cm -1 phonon modes drive an increase in ground state depletion magnitude in all photoexcitation locations, suggesting that they drive an increase in excited state species in pentacene through modification of either singlet fission or exciton transport dynamics. Amplification of both modes result in an increase in depletion at all photoexcitation locations (Fig. ). Because the oscillation periods of the 161 and 176 cm -1 modes are only 18 fs apart (207 fs and 189 fs, respectively) and our cross-correlation is 169 fs (Fig. ), we do not have the temporal resolution to distinguish between contributions from these two modes, and thus it is possible that either or both modes causes these changes. Moreover, their averaged ground state depletion amplitudes are only statistically significant at the (0, 0) excitation position at early times (Table ), and they are not statistically different at any time at (0, 2.7) and (2.7, 0) excitation positions. Based on these limitations, we will not separate dynamics that result from the amplification of each of these modes. We note that any changes in either dataset relative to the single pulse could be driven by only one of the phonon modes, both modes, or the combination of these two modes together could drive the dynamics. For clarity, we present a comparison of the single and 176 cm - 1 double pulse data in Figure , and the 161 cm -1 data is shown in Fig. . Figure 5. Averaged ground state bleach of the 1375 cm -1 peak for selected time windows for the single pulse (blue) and 176 cm -1 double pulse (green). Bar plots for 161 cm -1 are omitted here for clarity and are shown in Fig. .