Nonclassical photon statistics in single-molecule fluorescence at room temperature

The fluorescence of single terrylene molecules in a crystalline host is inv estigated at room temperature by scanning confocal optical microscopy Photo n arrival times are analyzed in terms of interphoton time distributions, se cond order correlation functions, and the variance of the photon number pro bability distribution. Antibunching at short times and bunching behavior fo r longer time is observed, associated with sub- and super-Poissonian statis tics, respectively. A rate-equation analysis of the molecular level populat ions indicates an accelerated reverse intersystem crossing.