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Fluorescence intensity decays of high-density polyethylene (HDPE) films have been studied by laserinduced fluorescence (LIF). An internally cavity-dumped dye laser synchronously pumped with a mode-locked argon-ion laser was used to excite the HDPE samples. The decay in the fluorescence intensity of HDPE film is due to the carbonyl present in the film, and was shown to be dependent on the power density of the incident UV light. The fluorescence intensity decay exhibits second-order kinetics. The experimental results obtained here demonstrate that the photostability of HDPE films can be characterized by the rate coefficient of the fluorescence intensity decay.

The excited-state proton transfer from 4-hydroxy-1-naphthalenesulfonate to urea has been studied in methanol at 25 °C. The decay of the acidic form is single-exponential for all urea concentrations. The proton acceptor concentration has been found to increase nonlinearly with the concentration of urea. The nonlinear behavior is explained by a model proposing urea monomers and, in particular, urea dimers to be the proton acceptors in methanol.

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