Regensburg 2007 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 22: POSTER: INTERNAL SYMPOSIUM Optical Spectrosopy
CPP 22.5: Poster
Wednesday, March 28, 2007, 16:00–18:30, Poster B
Tunneling Events in Methyl-Substiuted Terrylene in a Hexadecane Matrix — •Alfred Sigl1, Andre Gourdon2, Michel Orrit3, and Josef Friedrich1 — 1TUM, München, Germany — 2CEMES, Toulouse, France — 3MoNOS, Leiden, Netherlands
We investigated methyl-substituted terrylenes in a crystalline hexadecane matrix via hole-burning and single-molecule spectroscopy with the goal to detect single rotational tunneling events of the methyl group. A methyl group is a perfect tunneling system since there is no energy asymmetry. The rotational tunneling states correlate strictly with the nuclear spin states of the hydrogens. The hole burning experiments show a very unusual pattern: symmetric to the central hole appear two extremely sharp (200 MHz broad) antiholes, two broader antiholes and two sideholes. We associate the sharp antiholes, shifted by 1.3 GHz from the central hole, with the rotational tunneling states of the terrylene methyl group and the remaining features (5.1 and 6.4 GHz from the central hole) with a structural Two Level System involving the hexadecane lattice. The jumps in the frequency trajectories of single β-terrylene molecules reflect the 5.1 and 6.4 GHz features found in the hole-burning experiments. However, light-induced frequency jumps of single molecules corresponding with the 1.3 GHz features could not be detected. A possible reason could be that the high intensities in the single-molecule experiment pump the tunneling system to one of its substates.