Monday, June 29, 2009

Control of a magnetic Feshbach resonance with laser light

By Dominik M. Bauer, Matthias Lettner, Christoph Vo, Gerhard Rempe & Stephan Dürr

The capability to tune the strength of the elastic interparticle interaction is crucial for many experiments with ultracold gases. Magnetic Feshbach resonances [1, 2] are widely harnessed for this purpose, but future experiments [3, 4, 5, 6, 7, 8] would benefit from extra flexibility, in particular from the capability to spatially modulate the interaction strength on short length scales. Optical Feshbach resonances [9, 10, 11, 12, 13, 14, 15] do offer this possibility in principle, but in alkali atoms they induce rapid loss of particles due to light-induced inelastic collisions. Here, we report experiments that demonstrate that light near-resonant with a molecular bound-to-bound transition in 87Rb can be used to shift the magnetic field at which a magnetic Feshbach resonance occurs. This enables us to tune the interaction strength with laser light, but with considerably less loss than using an optical Feshbach resonance.

**Groupmeeting by Adam Weir**

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