Energy Levels in Chlorophyll and Electron Transfer Processes*,†

A brief account of the localized model for charge carrier generation in solid dyes is given, and generalized to include transfers of electrons and holes between unlike molecules. A part of the experimental basis for the localized model is the finding that the dye molecule sees its environment as a classical dielectric medium, even when it is composed of like molecules; since the effects of the environment on the ionization energy of chlorophyll are small, a close relationship can be inferred between laboratory energy levels and those effective in the chloro‐plast. The measured energy diagrams suggest a very low yield of charge carriers in either pure chlorophyll, but leave open the possibility of a substantial yield at an interface between chlorophylls a and b. The energy levels are consistent with the idea that charge carrier transfers between excited chlorophyll molecules and acceptors take place in the primary process.