Time resolved single molecule spectroscopy

A new method based on the calculation of autocorrelation functions for spectra measured at a high acquisition rate is developed to study spectral dynamics of single molecules. The technique allows for spectroscopy with time resolutions down to the luminescence lifetime. The method is used to study spectral diffusion in two-photon excitation spectra of diphenyloctatetraene molecules doped in an n-tetradecane crystal matrix. The diffusion is light induced, and is absent in one-photon excitation spectra. It has a "steplike" time behavior, different from gradual diffusion observed in glasses.