Heidelberg 2015 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 18: Poster: Ultra-cold atoms, ions and BEC (with Q)

A 18.28: Poster

Dienstag, 24. März 2015, 17:00–19:00, C/Foyer

High efficiency demagnetization cooling by suppression of light-assisted collisions — •Jahn Rührig, Tobias Bäuerle, Axel Griesmaier, and Tilman Pfau — 5. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, Stuttgart, 70569 , Germany

Demagnetization cooling [1] utilizes dipolar relaxations [2] that couple the internal degree of freedom (spin) to the external (angular momentum) in order to cool an atomic cloud efficiently [3,4]. Optical pumping into a dark state constantly recycles the atoms that were promoted to higher spin states. The net energy taken away by a single photon is very favorable since the lost energy per atom is the Zeeman energy rather than the recoil energy. As the density of the atomic sample rises the inherent involvement of the photons leads to limiting processes. In our previous publication [5] we have shown that light-assisted collisions are such an important limiting process. We present latest results on the suppression of light-assisted collisions in 52Cr by detuning the optical pumping light such that the Condon point coincides with the first node of the ground state wave function of two colliding atoms [6]. This leads to an increased cooling efficiency χ ≥ 17 as well as to increased maximum densities of n ≈ 1 · 1020 m−3.

[1]:A. Kastler, Le Journal de Physique et le Radium 11, 255 (1950).

[2]:S. Hensler et al. , Appl.Phys.B 77, 765 (2003).

[3]:S. Hensler et al. , Europhys. Lett. 71,918 (2005).

[4]:M. Fattori et al. , Nature Physics 2, 765 (2006).

[5]:V. Volchkov et al. , Phys. Rev. A 89, 043417 (2014).

[6]: K. Burnett et al. , Phys. Rev. Lett. 77, 1416-1419 (1996).

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