Fig. 4: Phenomenological quantum dynamics simulations.
a,c, Snapshots of the simulated wavepacket dynamics on the excited-state \(\left|{S}_{1}\right\rangle\) PES in the dimensionless coordinate plane defined by the Q− and Q+ effective modes in the absence (a) and presence (c) of a polar solvent. At early times <30 fs, comparable coherent wavepacket motion occurs in both cases, with the wavepacket symmetrically splitting along Q−. Coherent wavepacket motion persists until vibrational relaxation sets in on a 50 fs timescale. c, In the polar solvent, the build-up of the reaction field starts to tilt the PES, lowering the energy of one of the minima towards the solvated state. Black contour lines in a,c display the double-minimum PES and emphasize the effect of polar solvation (c) on the PES. b,d, Dynamics of the charge on the right (AR) and left (AL) acceptor sides of the molecule track charge separation upon optical excitation that forms two antiparallel dipoles in the molecule. b, In the absence of polar solvent, the dynamics are modulated only by vibronic coupling to Q+ which induces faint oscillations of the charge amplitude on the acceptors (inset). d, In polar solvent, additionally, the interaction with the building up reaction field results in charge asymmetry between the two arms. This induces a preferential localization of the charge on one arm of the molecule and forms a net dipole across the molecule.
