Why are plants green - relationships between pigment absorption and photosynthetic efficiency

In English The maximum efficiency of an optically thin photosynthetic system in converting solar radiation into chemical energy is theoretically considered as a function of the absorption spectrum of the photon-collecting pigment. The absorption band position giving maximum rate of power conversion is close to 700 nm in full sunlight and at somewhat shorter wavelength in weaker light. The chemical potential obtainable is decreased if the band is too wide. The effect of a 2nd absorption band (or accessory pigment) on potential is rather small.