MEASUREMENT OF OPTICAL DEPHASING OF A SINGLE TERRYLENE MOLECULE WITH NANOSECOND TIME RESOLUTION

We report on the investigation of temperature dependent optical dephas ing of single terrylene molecules in a p-terphenyl host crystal using two different techniques. The temperature dependence of the optical li newidth between 2 and 7.2 K can be described by an exponentially activ ated process with an activation energy Delta E = 18 +/- 2 cm(-1), whic h is attributed to optical dephasing of the electronic transition by s cattering of a pseudolocal mode. By measuring the fluorescence intensi ty autocorrelation function we demonstrate that the dephasing time of a single terrylene molecule can also be extracted from coherent transi ents (Rabi oscillations) appearing in the correlation function in the nanosecond time regime. These oscillations experience an increased dam ping at temperatures above 2 K due to pseudolocal mode-induced pure de phasing.