PROBING SINGLE-MOLECULE DYNAMICS

The room temperature dynamics of single sulforhodamine 101 molecules d ispersed on a glass surface are investigated on two different time sca les with near-field optics. On the 10(-2)- to 10(2)-second time scale, intensity fluctuations in the emission from single molecules are exam ined with polarization measurements, providing insight into their spec troscopic properties. On the nanosecond time scale, the fluorescence l ifetimes of single molecules are measured, and their excited-state ene rgy transfer to the aluminum coating of the near-field probe is charac terized. A movie of the time-resolved emission demonstrates the feasib ility of fluorescence lifetime imaging with single molecule sensitivit y, picosecond temporal resolution, and a spatial resolving power beyon d the diffraction limit.