The properties of the P D1 P D2 pair as a light absorber also differ from Chl D1 Pheo D1 pair. The highest absorption is observed only at the red and blue ends of the visible spectrum, see Figure . while in the energy window from 2.1 to 2.7 eV the P D1 P D2 pair absorbs only weakly. The pair thus appears to utilise visible light in a not very efficient manner, supporting the argument that the excitation of the P D1 P D2 pair happens via an energy transfer.