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Q: Quantenoptik und Photonik
Q 40: Gruppenberichte Quantengase II
Q 40.2: Group Report
Tuesday, March 8, 2005, 14:30–15:00, HU Kinosaal
Observation of Feshbach resonances and high phase space densities in a gas of 52Cr atoms — •Jürgen Stuhler1, Jörg Werner1, Axel Griesmaier1, Sven Hensler1, Andrea Simoni2, Eite Tiesinga2, and Tilman Pfau1 — 15. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart, Germany — 2National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8423, USA
We have evaporatively cooled a gas of 52Cr atoms in a crossed optical dipole trap to phase space densities up to 0.5. Observing the atom loss as a function of the applied magnetic offset field (4 to 600 G), we found fourteen Feshbach resonances (FR) with widths of up to 0.6 G. The absence of a hyperfine-structure eases the assignment of the experimental results. The eleven strongest FR build a complete set of all possible resonances up to second order in the magnetic dipole-dipole coupling for the decatriplett s-wave entrance channel. The positions of these FR are compared to results of multi-channel scattering calculations. By adjusting the s-wave scattering lengths, we are able to reproduce the positions of the FR and to determine the 2S+1Σg+ s-wave scattering lengths aS to a6=103 a0, a4=50 a0 and a2=−20 a0, respectively (a0=0.053 nm). The excellent agreement between theory and experiment is obtained without invoking other coupling mechanisms like second order spin-orbit coupling.