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SYC: Symposium Einzelne Atome, Ionen und Moleküle

SYC 2: Symposium Einzelne Atome, Ionen und Moleküle II

SYC 2.5: Vortrag

Donnerstag, 19. März 1998, 12:30–12:45, R 711

Time Resolved Single Molecule Spectroscopy — •Daniel Walser — Physical Chemistry Laboratory, Swiss Federal Institute of Technology, ETH Zentrum, 8092 Zurich, Switzerland

Fluorescence excitation spectroscopy on single guest molecules in low-temperature solids is the most sensitive method in the frequency domain for directly measuring the homogeneous line shape of optical transitions. In all systems investigated to date, the recording time of a single molecule line cannot be shorter than 10 ms in the best case. A new method based on the calculation of autocorrelation functions for spectra measured at a high acquisition rate is developed to study fast spectral dynamics of single molecules. Principally, the technique allows for temporal resolutions down to the luminescence lifetime. The method is applied to study spectral diffusion in two-photon excitation spectra of diphenyloctatetraene single molecules in an n-tetradecane Shpol’skii system. The diffusion is light induced and is absent in one-photon excitation spectra. Its temporal behavior is found to be different from the one observed in glasses and described by the standard two-level- system model. The new technique is promising to find a wide range of applications in the study of spectral dynamics on time scales from microseconds to hours.