Observation of an Optical Feshbach Resonance in ^88Sr

Travis Nicholson, Sebastian Blatt, Benjamin Bloom +2 more

Travis Nicholson, Sebastian Blatt, Benjamin Bloom +3 more

Pascal G. Mickelson, Y. N. Martinez de Escobar, Mi Yan +2 more

We have tuned the s-wave scattering length of 88Sr via an optical Feshbach resonance. Change in the rate of thermalization of atoms reveals a slight increase in the phase space density of the atom sample.

T. C. Killian, Mi Yan, B. J. DeSalvo +4 more

We use narrow-line photoassociation (PA) in an 88Sr Bose-Einstein condensate to control condensate collapse and expansion with an optical Feshbach resonance. We also accesses a regime of coherent single-color PA in which we observe atom-molecule Rabi oscillations and create condensates of excited-state molecules.

Matthias Theis, Rudolf Grimm, Johannes Hecker Denschlag

Pascal G. Mickelson

This thesis describes trapping and evaporative cooling of ultracold 87Sr and 88Sr mixtures in an optical dipole trap to produce the first Bose-Einstein condensate (BEC) of 88Sr. Furthermore, this work presents thermalization studies that characterize the scattering properties of these ultracold strontium samples. Such ultracold atomic gases have become an important area of research because of their potential for improving optical frequency standards and for realizing quantum computation using neutral atoms. A BEC of 88Sr is particularly interesting because the small value of its background s-wave scattering length may enable the use of optical Feshbach resonances to create two-dimensional solitons. However, the small scattering length for 88Sr also hinders efficient evaporative cooling in the optical dipole trap, a necessary step to producing a BEC. Experiments with other ultracold gases have successfully overcome this hurdle by mixing in a second atomic species which, by introducing stronger interactions with the weakly interacting species, enables evaporation to colder temperatures via sympathetic cooling. For this work, we use 87Sr to sympathetically cool 88Sr during forced evaporation to quantum degeneracy.\nPrevious experiments in the Killian Lab characterized 88Sr in detail. Here, I emphasize the new or improved aspects that have allowed trapping and cooling of the mixtures of 87Sr and 88 Sr: trapping of 87Sr by itself, spectroscopic measurements of all the stable strontium isotopes to guide the trapping of isotopic mixtures, imaging of both 87Sr and 88Sr, and the various trade-offs necessary to simultaneously trap 87Sr and 88Sr. Finally, I discuss how the thermalization studies of the scattering properties of the isotopes guide the forced evaporation of mixed isotope samples. These efforts result in the production of the BEC of 88Sr, but they also point the way to future studies of fermionic quantum degeneracy in 87Sr and to the rich physics of mixed species ultracold atomic systems.