J. Herbig

Three-body recombination at large scattering lengths in an ultracold atomic gas.

We study three-body recombination in an optically trapped ultracold gas of cesium atoms with precise magnetic control of the s-wave scattering length a. At large positive values of a, we measure the dependence of the rate coefficient on a and confirm the theoretically predicted scaling proportional to a(4). Evidence of recombination heating indicates the formation of very weakly bound molecules in the last bound energy level.

Observation of Feshbach-like resonances in collisions between ultracold molecules.

We observe magnetically tuned collision resonances for ultracold Cs2 molecules stored in a CO2-laser trap. By magnetically levitating the molecules against gravity, we precisely measure their magnetic moment. We find an avoided level crossing which allows us to transfer the molecules into another state. In the new state, two Feshbach-like collision resonances show up as strong inelastic loss features. We interpret these resonances as being induced by Cs4 bound states near the molecular scattering continuum. The tunability of the interactions between molecules opens up novel applications such as controlled chemical reactions and synthesis of ultracold complex molecules.

Optimized production of a cesium Bose–Einstein condensate

We report on the optimized production of a Bose–Einstein condensate of cesium atoms using an optical trapping approach. Based on an improved trap loading and evaporation scheme we obtain more than 105 atoms in the condensed phase. To test the tunability of the interaction in the condensate we study the expansion of the condensate as a function of scattering length. We further excite strong oscillations of the trapped condensate by rapidly varying the interaction strength.

Efficient creation of molecules from a cesium Bose-Einstein condensate

We report a new scheme to create weakly bound Cs2 molecules from an atomic Bose-Einstein condensate. The method is based on switching the magnetic field to a narrow Feshbach resonance and yields a high atom-molecule conversion efficiency of more than 30%, a factor of three higher than obtained with conventional magnetic-field ramps. The Cs2 molecules are created in a single g-wave rotational quantum state. The observed dependence of the conversion efficiency on the magnetic field and atom density shows scattering processes beyond two-body coupling to occur in the vicinity of the Feshbach resonance.

Bose-Einstein condensation of optically trapped cesium

Summary form only given. Bose-Einstein condensation of cesium atoms is achieved by evaporative cooling using optical trapping techniques. The ability to tune the interactions between the ultracold atoms by an external magnetic field offers intriguing features for potential applications.

Trapping and interactions of an ultracold gas of CS/sub 2/ molecules

We investigate dynamics and interactions of Cs/sub 2/ dimers in a CO/sub 2/-laser dipole trap. Starting with a Bose-Einstein condensate (BEC) of 2.2*10/sup 5/ Cs atoms, we create ultracold molecules in a single, weakly bound quantum state by sweeping the magnetic field across a narrow Feshbach resonance.

Bose‐Einstein‐Kondensation mit Cäsium

Seit der ersten Erzeugung eines Bose-Einstein-Kondensates (BEC) vor einigen Jahren konnten nur wenige weitere atomare Spezies in diesen Materiezustand versetzt werden. Physikern an der Universitat Innsbruck ist dies nun erstmals mit Casium gelungen [1]. Casium zeigt ein exotisches Wechselwirkungsverhalten, das neuartige Experimente in Kondensaten ermoglicht.

Evaporative cooling in optical dipole traps

Summary form only given. Optical dipole traps operating with laser light very far from resonance can provide conservative trapping potentials with interesting new features for evaporation experiments. We explore the prospects of evaporative cooling in various trapping schemes.