Roles played by an oxygen atom and out-of-plane high-frequency vibrational modes of a dibenzofuran molecule in the nonradiative deactivation of the lowest triplet state

We have studied the deactivation of the triplet sublevels s = z, y, and x of the lowest triplet state T ₁ ^s of the dibenzofuran molecule, which is determined by radiative (dipole) and nonradiative (degradation) transitions with the rate constants K _rad ^s and K _dg ^s . The main attention is paid to the nonradiative transitions T ₁ ^s ? S ₀ from the in-plane spin states (s = z, y), which are determined by the intramolecular interaction along the coordinates of out-of-plane vibrational modes. The roles played by the many-electron atom (oxygen) and high-frequency out-of-plane vibrational modes in the intramolecular interaction have been evaluated theoretically. Estimates of K _dg ^s based on three known approaches (three models) that describe the nonradiative transition in the approximation of adiabatic and nonadiabatic interactions are presented.