Efficiencies of O2(1Σ+g) and O2(1Δg) formation in the primary steps of triplet state photosensitization in solution

Abstract The primary steps of triplet state (T 1 ) sensitization of singlet oxygen O 2 ( 1 Σ + g ) and O 2 ( 1 Δ g ) by phenalenone (PH) and benzophenone (BP) have been investigated in carbon tetrachloride by time-resolved measurements of the phosphorescence of T 1 , O 2 ( 1 Σ + g ) and O 2 ( 1 Δ g ). Besides lifetimes, the detailed analysis of the transient curves yields absolute efficiencies a of O 2 ( 1 Σ + g ) and b of O 2 ( 1 Δ g ) formation in the primary energy transfer step from T 1 to O 2 . For PH a = 0.62 and b =0.37, for BP a =0.11 and b =0.26 were found. Collisional deactivation of O 2 ( 1 Σ + g ) by carbon tetrachloride, benzene, cyclohexane, trimethylpentane and methanol produces O 2 ( 1 Δ g ) with efficiency c ⩾0.95.