Some Photoelectric Properties of Chlorophyll

Both chlorophyll a and methyl chlorophyllide a have been found to be photoconductive in films deposited from solvents. The photoconductivity of methyl chlorophyllide a resembles that of some cyanine dyes in having two time constants for rise and decay, one less than a second, and the other of the order of several minutes. The action spectrum of the ``fast'' photoconductivity is similar to the absorption spectrum of the pigment, the red peak falling at 6740 A. Both pigments sensitize photoconductivity in cadmium sulfide films, and the contact potential difference at the interface is of the correct sign to permit electron transfer from dye to crystal. These properties give some support to Katz's hypothesis regarding the primary process in photosynthesis.