Berlin 2001 – wissenschaftliches Programm

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Q: Quantenoptik

Q 17: Poster: Cooling and Trapping

Q 17.30: Poster

Mittwoch, 4. April 2001, 12:30–15:00, AT2

Investigation of long range states of highly excited molecules - a scheme to create cold Na₂ molecules? — •Tanja Laue, Christian Samuelis, Horst Knöckel, and Eberhard Tiemann — SFB 407, Institut für Quantenoptik, Universität Hannover

Laser cooling of atoms is a well established technique to reach sub mK temperatures. But the extension to molecules is generally not posssible. One way to create cold ground state molecules is photoassociation of cold trapped atoms. Two colliding atoms absorb a photon and create an excited molecule at long range. The de-excitation leads back to two atoms with changed kinetic energy but also to a small fraction of cold ground state molecules. The formation of these cold molecules is quite efficient if the excited molecular state has a good Franck-Condon overlap with ground state wave functions. This can be the case for excited states with a double well structure (example: Cs₂ [1]).
A calculation for Na₂ [2] shows that such a double-well potential (6 ¹Σ_g⁺) which correlates to the 3s+5s asymptote exists. We setup a molecular beam experiment where we prepare long range molecules in the A ¹Σ_u⁺ via Franck-Condon pumping [3] and then use a coherent process to excite to the second well of the 6 ¹Σ_g⁺ state. The status of the experiment will be presented.

[1] A. Fioretti, D. Comparat, A. Crubellier, O. Dulieu, F. Masnou-Seeuws, and P. Pillet, Phys. Rev. Lett. 80, 4402 (1998)

[2] M.-L. Almazor, O. Dulieu, M. Elbs, E. Tiemann, and F. Masnou-Seeuws, Eur. Phys. J. D 5, 237 (1999)

[3] E. Tiemann, H. Knöckel, H. Richling, Z. Phys. D 37, 323 (1996)