PROBING INDIVIDUAL MOLECULES WITH CONFOCAL FLUORESCENCE MICROSCOPY

Confocal fluorescence microscopy coupled with a diffraction-limited la ser beam and a high-efficiency detection system has been used to study the diffusive movement and emission process of individual fluorescent molecules in the liquid phase at room temperature. The high detection sensitivity achieved at fast data acquisition speeds (greater than 1 kilohertz) allows real-time observation of single-molecule fluorescenc e without statistical analysis. The results show fluorescence-cycle sa turation at the single-molecule level and multiple recrossings of a si ngle molecule into and out of the probe volume as well as the triplet state.