München 2004 – scientific programme

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MO: Molekülphysik

MO 2: Experimentelle Techniken, Kalte Moleküle

MO 2.5: Talk

Monday, March 22, 2004, 12:30–12:45, HS 332

Paul trap for investigation of fluorescent nanoparticles — •Kirstin Wohlfart and Olliver Benson — Nano Optics, Institut für Physik, Humboldt-Universität zu Berlin, Hausvogteiplatz 5-7, 10117 Berlin, Germany

In order to study intrinsic properties of single nanoparticles and macromolecules the elimination of interaction between the particle and their environment is desirable. This can be achieved by investigation of single, charged particles in electrodynamic traps.

A Paul trap setup for trapping fluorescent nanoparticles charged by electrospray ionisation was developed. The setup has an optimized optical sensitivity which allowed the detection of single semiconductor nanocrystals or labeled macromolecules. In first test experiments the trap was operated under atmosperic pressure and ambient conditions. Microscopy and spectroscopy of spherical trapped particles in the micron range was routinely feasible.

The theory of particle motion in a quadrupole trap was extended to include damping of particle motion in air. It is shown that the shift of the particle position due to an external static electric field is a simple tool to determine both size and specific charge of the trapped particle.