We exploit the strong excitonic coupling in a superradiant trimer molecule to distinguish between long-lived collective dark states and photobleaching events. The population and depopulation kinetics of the dark states in a single molecule follow power-law statistics over 5 orders of magnitude in time. This result is consistent with the formation of a radical unit via electron tunneling to a time-varying distribution of trapping sites in the surrounding polymer matrix. We furthermore demonstrate that this radicalization process forms the dominant pathway for molecular photobleaching.
Applied Optics group, Faculty of Science & Technology and MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, NL-7500AE Enschede, the Netherlands. j.p.hoogenboom@utwente.nl
