Fluorescence lifetime measurement of dibenzofuran and monochlorodibenzofuran

The fluorescence lifetime of dibenzofuran and monochlorodibenzofuran was measured directly using a picosecond distributed-feedback dye laser and a fast-response microchannel-plate photomultiplier. The fluorescence lifetimes for dibenzofuran and monochlorodibenzofuran were determined to be 10.8±0.5 ns and ca. 1 ns, respectively, suggesting that the fluorescence quantum yield is reduced 10-fold by intersystem crossing induced by a chlorine atom in a dibenzofuran molecule. These findings highlight the advantages of a picosecond laser for the efficient multiphoton ionization of polychlorinated dibenzofurans.