Nonlinear Fluorescence Reabsorption in Excimer-Forming Crystals by Electronically Excited Molecules

Anomalous slowing down of fluorescence decay at high excitation density has been observed in pyrene and $\alpha$-perylene crystals, and attributed to nonlinear fluorescence reabsorption by electronically excited molecules. This phenomenon may have various implications in studies of condensed phases at high levels of optical exciation.