Exciton interactions in naphthalene single crystals

The decay of the fluorescence and T—T absorption change in naphthalene crystal induced by an intense electron pulse is measured and analyzed. It is shown from the optical absorption measurement that the decay of the triplet excitons follows bimolecular reaction kinetics. The decay of the fluorescence is found to be very much dependent on the intensity of the electron pulse. The result is analyzed with reaction kinetics comprising the singlet—singlet, singlet—triplet, and triplet—triplet annihilation processes. The values of annihilation rate constants are obtained at 77, 200, and 298 K. The singlet—triplet annihilation rate constant is calculated under Förster's long‐range resonance transfer scheme by employing the results of T—T absorption of naphthalene crystal. Good agreement is obtained for γST. It is demonstrated that the annihilation of the singlet exciton is diffusion controlled.