Deactivation mechanism of photoexcited 9-phenylacridine in methanol

Electronic deactivation processes of excited 9-phenylacridine (9-PA) have been investigated in methanol where photoreduction occurs under UV irradiation. The fluorescence lifetime τ F and yield Φ F increase with decreasing temperature, whereas the yield Φ ST of the lowest triplet state T 1 (π, π * ) and the yield Φ R of the semiquinone radical of 9-PA decrease