Regensburg 2007 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 6: Dynamics of Molecular Systems

CPP 6.2: Talk

Monday, March 26, 2007, 14:45–15:00, H47

Low-temperature spectral dynamics of single TDI molecules in alkane matrixes — •Sebastian Mackowski, Stephan Wörmke, Moritz Ehrl, and Christoph Bräuchle — Department of Chemistry and Biochemistry and Center for Nanoscience, Ludwig-Maximilian-University, D-81377 Munich, Germany

We use vibronic excitation approach to study the low-temperature (1.6K) fluorescence dynamics of the single TDI molecules in alkane matrixes. Four hosts were used, characterized with different length and parity: heptane, hexane, pentadecane and hexadecane. For every matrix, fluorescence trajectories of several tens of single molecules were measured. In the case of long-chain alkanes (pentadecane and hexadecane), the fluorescence of single TDI molecules has been found to be stable, showing only occasional spectral jumps of moderate energy (<10cm-1). An average time between the jumps is 10 seconds and the jumps occur between well resolved levels. We have not observed any difference between the two matrixes. On the other hand, the spectral dynamics of TDI molecules embedded within the short-length alkane matrixes (heptane and hexane) is dramatically different. In these cases the spectral jumps are much more frequent, with average time between the two jumps being less than 1 second. In addition, we also observe significant, threefold increase in average energy of the jump. No qualitative differences between the two matrixes with short chain length were observed. The results suggest that matrixes composed of short chain molecules are more susceptible for translations and/or rotations which influence the spectral properties of single chromophores.