Hamburg 2009 – scientific programme

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MO: Fachverband Molekülphysik

MO 23: Molekülphysik Poster 2

MO 23.8: Poster

Thursday, March 5, 2009, 16:30–19:00, VMP 8 Foyer

Spectroscopy of thin molecular films under ultrahigh vacuum conditions using tapered optical fibres — •Ariane Stiebeiner, Olga Rehband, David C. Papencordt, Ruth Garcia-Fernandez, and Arno Rauschenbeutel — Abteilung QUANTUM, Institut für Physik, Johannes Gutenberg-Universität Mainz, 55099 Mainz

The guided modes of sub-wavelength-diameter air-clad optical fibres exhibit a pronounced evanescent field. The absorption of light by molecules deposited at the fibre surface is therefore readily detected by measuring the fibre transmission. We have shown that the resulting absorption for a given surface coverage can be orders of magnitude higher than that for conventional surface spectroscopy. The measurements were performed on sub-monolayers of 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) molecules at ambient conditions, revealing the agglomeration dynamics on a second to minutes timescale [1].

We set up a new apparatus integrating the ultrathin fibre under ultrahigh vacuum (UHV) conditions in order to gain better control over the system. Firstly, this arrangement enables us to produce an homogeneous flux of molecules for deposition onto the ultrathin fibre waist. Furthermore, it allows us to desorb pollutants from the fibre and thus to work with a better defined surface. The measured absorption spectra of the deposited molecules and their time evolution are compared with the results obtained at ambient conditions.

We gratefully acknowledge financial support by the Volkswagen Foundation, the ESF, and the EC.

[1] F. Warken et al., Opt. Express 15, 11952-11958 (2007)