Energy transfer in the course of triplet state quenching of aromatic hydrocarbons by nitroxyl radicals

Quenching of triplet states of aromatic hydrocarbons by nitroxyl radicals has been investigated by the flash photolysis method. There are two different mechanisms of triplet quenching: quenching occurs via enhanced intersystem crossing on exchange interaction with the radical for the triplet states of aromatic hydrocarbons which have low triplet energy (E_T < 14700 cm^?1); for very high triplet energies, energy transfer from the triplet molecule to the nitroxyl radical occurs. The energy of the excited nitroxyl radical was estimated to be 18000 cm^?1.