[Photoluminescence of singlet oxygen in solutions of chlorophylls and pheophytins]

With the use of mechanical phosphoroscopes the photoinduced luminescence of singlet oxygen (1270 nm) have been found in air saturated solutions of chlorophyll a, bacteriochlorophyll a, protochlorophyll and pheophytins in CCl4, CS2, and freon 112. The excitation spectra of the luminescence coincide with the absorption spectra of the pigments. The relative quantum yields of the luminescence are determined, the data are used for calculation the probablities of intersystem crossing in pigment molecules. All the pigments are shown to quench 1O2, the rate constants of the quenching are measured. The quenching efficiency of the chlorophylls increases with reduction of the semiisolated double bonds, reduction of these bonds in molecules of the pheophytins decreases the constants of the quenching.