Higher Triplet Excited States of Benzophenones and Bimolecular Triplet Energy Transfer Measured by Using Nanosecond–Picosecond Two‐Color/Two‐Laser Flash Photolysis

The lifetimes of benzophenone in the higher triplet excited state (BP(T n )) and several BP derivatives in the T n states were measured directly to be τ T n =37±7 ps and 20–33 ps, respectively, by using the nanosecond–picosecond (ns–ps) two‐color/two‐laser flash photolysis method. Based on the direct measurements of τ T n of BP(T n ), the triplet energy transfer (TET) from BP(T n ) to quenchers (Q), such as carbon tetrachloride (CCl 4 ), benzene (Bz), and p ‐dichlorbenzene (DCB), was investigated. The fast TET from BP(T n ) to Q can be attributed to the lifetime‐dependent quenching process, according to the Ware theoretical model of the bimolecular energy transfer reaction. The contribution of the lifetime‐dependent term on k TET was 27, 60, and 86 % for CCl 4 , Bz, and DCB as the Q of BP(T n ), respectively, indicating that the TET from BP(T n ) to Q is influenced not only by τ T n , but also by the size of Q.