exciplex by translating one of the monomers in the xy plane parallel to both monomers. During the scanning, both monomers' internal coordinates and their interplanar distance (3.5 Å) are fixed, and their TDMs are aligned with the horizontal x-axis. As shown in Figure , the energy of the LE states, E %& +44 and E %& R+11S , are nearly identical and not sensitive to their relative position, as the monomer geometries are fixed at their S1 minimum during the translation.