The excited-state dynamics of the radical cations of perylene (PE •+ ), tetracene (TE •+ ), and thianthrene (TH •+ ), as well as the radical anions of anthraquinone (AQ •-) and tetracenequinone (TQ •-), formed by γ irradiation in low-temperature matrices (PE •+ , TH •+ , AQ •-, and TQ •-) or by oxidation in sulfuric acid (PE •+ , TE •+ , and TH •+ ) have been investigated using ultrafast pump-probe spectroscopy. The longest ground-state recovery time measured was 100 ps. The excited-state lifetime of PE •+ is substantially longer in low-temperature matrices than in H 2 SO 4 , where the effects of perdeuteration and of temperature on the ground-state recovery dynamics indicate that internal conversion is not the major decay channel of PE •+ *. The data suggest that both PE •+ * and TE •+ * decay mainly through an intermolecular quenching process, most probably a reversible charge transfer reaction. Contrarily to AQ •-*, TQ •-* exhibits an emission in the visible which, according to theoretical calculations, occurs from an upper excited state.
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