Influence of Vibrational Excitation of Triplet Molecules of Anthraquinone on the Photochemical Processes in Gas Mixtures with Amines

Abstract

By the quenching of the delayed fluorescence (DF) of anthraquinone vapors by aliphatic amines (diethylamine, dibutylamine, cyclohexylamine) and pyridine the photoinduced processes proceeding with the participation of vibrationally excited triplet molecules of anthraquinone have been investigated. The DF quenching‐rate constants Kq varying from 1·106 sec−1·torr−1 in mixtures with diethylamine to 7·103 sec−1·torr−1 in mixtures with pyridine have been estimated. A correlation between the values of Kq and the ionization potentials of foreign gases confirming the important role of interactions with charge transfer in the quenching of triplet molecules in the gas phase has been established. The influence of other relaxation processes on the DF quenching is considered. It is shown that the intermolecular vibrational relaxation in the T1 triplet state leading to the establishment of relaxation equilibrium at a vibrational temperature Tvib considerably increasing the medium temperature is the fastest process among the biomolecular processes (rate constants KcolV > 106 sec−1·torr−1 > Kq). The values of Tvib and the vibrational energies Evib of the triplet molecules after the energy exchange in the collisional complex have been estimated. It has been concluded that the photochemical reaction yield is determined by the intermolecular processes proceeding in the T1 state at a vibrational equilibrium characterized by high values of Tvib. The influence of Evib of triplet molecules on the DF quenching rates at a photoinduced electron transfer is considered.