Super and sub-Poissonian photon statistics for single molecule spectroscopy

Full Text:Single atoms in the process of resonance fluorescence exhibit well known elects of photon anti-bunching and related sub-Poissonian photon statistics. These behaviors indicate that photon emission events from a single source are correlated. Tn recent years sub-Poissonian statistics was observed for single molecules embedded in condensed phase environments. Due to different types of interactions between the molecule and its environment, sub-Poissonian statistics of single molecules is very different than that found for simple atomic systems. In our talk we will investigate the relation between spectral diffusion, and single molecule photon statistics. Transitions between quantum (sub-Poissonian) and classical (super-Poissonian) behaviors is found, as well as a transition between a fast modulation limit (motional narrowing limit) and a slow modulation limit. In particular we obtain an exact expression for Mandel's Q parameter for a single molecule undergoing a Kubo-Anderson spectral diffusion process and interacting with a cw laser field. A Lower bound on Q is found. We show that there exists an optimal Rabi frequency on which the quantum fluctuations become strongest. Comparison to experiment is made