Here, I is intensity, E is excitation energy, N sn = 151 is the number of selected snapshots, N st = 20 is the number of excited singlet states, E i,α and f i,α are the excitation energy and oscillator strength, respectively, for the S 0 → S i transition, for snapshot α, and γ = 0.18598 eV (1500 cm -1 ) is a broadening parameter (the same value as used in ref. 47). The brightest state among the nπ * states (S 1 -S 4 ) was selected as the initial state for the surface hopping calculations. We should recall here that the monomeric S 0 → S 1 transition is dark for the ground-state minimum geometry, but it acquires nonzero (albeit small) oscillator strength upon geometric distortions resulting from ground-state MD simulations in our case. In the tetramer, the nπ * monomeric state (S 1 ) is split into four states, S 1 -S 4 . Comparing oscillator strengths of the transitions to these exciton states from the ground state of the tetramer (for a given initial geometry), we select the state with the highest oscillator strength as an initial state for a surface hopping run.