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Abstract: The UV absorption cross-sections and the rate coefficients for the ozonolysis of styrene, α-methylstyrene, β-methylstyrene, 2-methylstyrene and indene have been investigated. The absorption spectra were measured using a diode array spectrometer over the wavelength range 260–310nm at 328K. Large absorption cross-sections (∼10−18 cm2 molecule−1) were observed for the investigated compounds over the wavelength range 260–280nm, while their absorption cross-sections decreased sharply above 290nm with values of about 10−20 to 10−21 cm2 molecule−1 around 310nm. The rate coefficients for the reactions of the aromatic compounds studied and O3 measured in a simulation chamber using both absolute and relative methods at 295±3K and atmospheric pressure were (in 10−17 cm3 molecule−1 s−1): (1.5±0.3), (1.8±0.4), (3.1±0.6) and (16±4) for styrene, α-methylstyrene, 2-methylstyrene and indene, respectively. The data obtained were used to estimate the lifetimes of the investigated compounds. [Copyright &y& Elsevier]