Osnabrück 2002 – wissenschaftliches Programm
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A: Atomphysik
A XIX: HV XIX
A XIX.1: Hauptvortrag
Freitag, 8. März 2002, 11:00–11:40, HS 22/B01
Optical dipole-dipole coupling between two individual molecules — •Christian Hettich1, Carmen Schmitt1, Jan Zitzmann2, Sergei Kühn2, and Vahid Sandoghdar2 — 1Department of Physics, University of Konstanz, Konstanz, Germany — 2Physical Chemistry Laboratory, ETH, Zurich, Switzerland
Here we report the observation of coherent optical dipole-dipole coupling of two individual molecules.
We study single fluorescent molecules in solid matrices at low temperatures that show nearly lifetime limited linewidths and very high quantum yields. This together with the well-defined position of a single molecule in a crystal makes it an ideal candidate for a number of experiments.
Dipole interaction between single molecules can be studied if the molecules meet two criteria: 1) they have to be very close to each other and 2) their resonance frequencies have to be similar. We found two such molecules and by varying the intensity and frequency of the excitation laser we have seen that at high intensities a new resonance appears near the average frequency of the two molecules. At this resonance we observed photon bunching in the fluorescence which is an evidence that this resonance belongs to a two photon excitation into the state where both molecules are excited. We present the experimental data and a theoretical description by solving the master equation for the total system.