FEMTOSECOND STUDY OF RELAXATION OF HYDRATED CHLOROPHYLL-A AGGREGATE IN HYDROCARBON SOLUTION

Electronic relaxation of chlorophyll a-water adduct in 3-methylpentane solution has been studied by using femtosecond absorption recovery an d picosecond fluorescence measurements. A fast initial lifetime of 1.5 ps and a slower lifetime component of 35 ps are observed. The fast de cay of 1.5 ps is assigned to efficient internal conversion and energy transfer and trapping in the chlorophyll a-water adduct. The slower li fetime component is assigned to a localized excitation in the aggregat e. No indication of exciton annihilation is observed in the excitation intensity range from 7 x 10(10) to 1 X 10(17) photons/ (pulse cm2).