The population dynamics and the fitting results are plotted as black solid and red dashed lines, respectively. The detailed fitting procedure is described in the SI. By this, we are able to resolve two time-constants of population dynamics, 13 and 561 fs. The fast component of 13 fs presents the population increase of TT state within 100 fs, which agrees to the experimental observation of 100 fs in pentacene crystals. In addition to this fast rise component, the population of TT state slowly increases with the subsequent time-constant of 561 fs. We also perform the data analysis of the population with CT state and the result shows the timescale of 56 and 889 fs, which is close to the case without the CT state. In the modeling, we employed 6 cm -1 of the excitonic interaction between singlet and triplet-pair state, which is too weak to drive the ultrafast process of the SF in a time range of 100 fs. To obtain the quantum coherent information, we subtract the magnitude of the kinetics and plot the residuals as blue solid line in Fig. (a). We observe a clear evidence of coherent oscillations. We further perform the Fourier transform of residuals and plot the results in Fig. ). We resolve the peaks at 109, 259, 434 and 996 cm -1 . We understand that the highfrequency and low-frequency modes of 996, 109 cm -1 quantitatively agree to the frequencies of Holstein and Peierls modes in our model. However, the origin of the two peaks at 259 and 434 cm -1 is still unclear. For this, we need to perform further data analysis. In addition, there is a lowfrequency mode of 22 cm -1 in Fig. (b), which is caused by the imperfect fitting of low-frequency mode. For the comparison, we also plot the FFT results of model with CT state in the SI and it shows the resolved peaks at 109, 196, 259 and 996 cm -1 .