Regensburg 2004 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 9: Single Molecule Spectroscopy

CPP 9.2: Talk

Monday, March 8, 2004, 14:15–14:30, H 38

Single molecule spectroscopy at cryogenic temperatures using vibronic excitation and dispersed fluorescence detection — •Alper Kiraz, Moritz Ehrl, Christoph Bräuchle, and Andreas Zumbusch — Department Chemie, Ludwig-Maximilians Universität München, Butenandtstr. 11, D-81377 München, Germany

Low temperature single molecule spectroscopy experiments often rely on excitation from the purely electronic zero-phonon-line and collecting the Stokes shifted fluorescence[1]. A major problem of this technique however, is that only exceptionally photostable systems can be studied. Because the absorbing zero-phonon-line is so narrow, already small spectral jumps (>30 GHz) in absorption lead to a loss of the excitation.

Here we report vibronic excitation combined with spectrally resolved zero-phonon-line detection as a novel technique for single molecule spectroscopy at cryogenic temperatures. In contrast to zero-phonon-line excitation, vibronic excitation benefits from large absorption bands (broadened by 1-10 ps lifetimes and phonon sidebands) allowing for investigation of large spectral jumps. We observed single terrylenediimide molecules in both n-hexadecane (Shpol’skii matrix) and PMMA (polymer), and recorded spectral jumps as large as 80 cm⁻¹ with 1 sec time resolution[2].

This technique promises applications in spectroscopy of a wide-range of single molecules in amorphous hosts including fluorescing proteins. It also allows for investigation of the emission linewidth of a single molecule’s zero-phonon-line.

[1] A.-M. Boiron et al., Chem. Phys. 247, 119 (1999).

[2] A. Kiraz et al., J. Chem. Phys. 118, 10821 (2003).