Energy dependence of optically induced exciton fission

A general discussion of the kinematics of optically induced fission in organic crystals is presented. Explanations are given for the nonoccurrence of this phenomenon in certain systems, and a theoretical interpretation is offered for the photon energy dependence of the magnetic field effect on the prompt fluorescence of solid tetracene at 77°K. The structure observed by Moller and Pope below 30 000 cm−1 is interpreted as a progression in the totally symmetric C–H stretching mode, where the Franck-Condon vibrational coupling constant g for the correlated pair singlet-triplet transition is found to be of the order of unity. Several experiments to test the predictions of the theory are suggested.