Abstract
We have solved the density matrix equation for mutual triplet annihilation in some special cases. The solution allows a simple calculation of the magnetic field dependence of the annihilation rate γs for homofusion at high and intermediate magnetic fields and for heterofusion in the high field limit. In our experiments we have measured the magnetic field anisotropy of the guest delayed fluorescence in doped anthracene and naphthalene crystals. By using the resonance condition for heterofusion, the positions of the resonance peaks have been calculated. A comparison of the measured and calculated resonance directions shows that tetracene enters the anthracene lattice substitutionally oriented, whereas the orientation of pyrene molecules in naphthalene differs slightly from the substitutional one. Furthermore, we have shown that in the latter case the host–guest annihilation gives rise almost exclusively to guest delayed fluorescence, although the excitation of the host singlet state is energetically possible.
Published Version
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