Absorption properties of aggregated (dimeric) chlorophyll

The absorption spectrum of an aggregated form of chlorophyll a in ethanol is given. This aggregate, which could be a dimer, has major absorption maxima at 682, 648, and 455 mμ. A geometry is suggested for it, based upon the spectral changes which result from aggregation. The shape of the red band of the dimer, and an estimate of dimer concentration (relative to total chlorophyll) is given for two different kinds of algae. There is good correlation between the absorption properties of the aggregate and the ligh-induced changes in absorption observed in photo-synthetic material. © 1961.