PHOTOPRODUCTION OF IONS FROM CHLOROPHYLL α IN SOLUTION STUDIED BY FLASH PHOTOLYSIS and PHOTOCONDUCTIVITY

— Ionic species were detected electrically on flash excitation of chlorophyll α following rapid production of the triplet state of the pigment. The action spectrum of photocurrent agreed well with the absorption bands of the pigment in the visible region; the threshold for the formation of ionic species in acetonitrile was 1.8 eV. Oxygen gas introduced into the solution completely prevented the appearance of the triplet and ionic species. The latter are suggested to result from electron-transfer between the triplet pigments. Decay processes of the ionic species varied markedly with changes in the solvent polarity. Direct photo-ionization of the pigment could be observed by UV excitation in some non-polar solvents.