Exciton band structures in 2D aggregates of cyanine dyes

Herring‐bone structures (see figure, where the rectangles are the dye molecules and the arrows indicate the oscillation of the transition dipoles) can be classified on the basis of the angle of mutual orientation of the two molecules per unit cell. Those with small angles showing nearly resonant fluorescence emission from the most redshifted transition (J‐aggregates). magnified image