Singlet Exciton Collisions in Crystalline Anthracene

We present a new determination of the singlet‐singlet annihilation rate constant in crystalline anthracene based on simultaneous measurements of the fluorescence quantum yield and of the fluorescence decay. Optical excitation was achieved by the second harmonic of a ruby laser. A detailed kinetic scheme for singlet‐exciton kinematics is discussed with particular emphasis on the role of metastable exciton states in an organic molecular crystal. Finally, we consider the problem of stimulated emission and light amplification from crystalline anthracene and explore the possibility of utilizing this molecular crystal as an active optical element in a molecular‐crystal laser.