Event Time: Friday, February 23, 2024 | 9:30 am - 11:30 am
Event Location:
Henn 318
Add to Calendar 2024-02-23T09:30:00 2024-02-23T11:30:00 Atom-Atom, Atom-molecule and molecule-molecule collisions at ultra-cold and room temperature Event Information: Abstract:  This thesis describes experiments with magnetically and optically trapped  ultra-cold gases of 6Li and 85,87Rb atoms. We describe three distinct areas of investigation, with a common theme of probing collisions: the production of deeply bound 6Li2 dimers and a study of their reactive collisions, the use of ultra-cold atoms as a pressure sensor by measuring the loss rate due to collisions with background gases at room temperature, and progress towards investigating heteronuclear collisional resonances between ultra-cold 6Li and 85,87Rb. We report on the production of deeply bound triplet a(13Σ+u ) 6Li2 molecules in a single quantum state by stimulated Raman adiabatic passage. The ensemble lifetimes for these molecules were found to be limited by dimer- dimer collisions whose rate depends on the ro-vibrational state of the collision partners. The loss rate observed follows a universal prediction for the |v = 0, 5, 8; N = 0, 2⟩ states, and remarkably, a sub-universal rate for the |v = 9; N = 0⟩ state. We find that molecules in the ground state of the triplet potential are also collisionally unstable, consistent with theoretical predictions that molecules in any of the triplet levels are chemically unstable and decay due to a barrier-less trimer formation process.  We also report on a comparative measurement of the cross section for trap loss inducing collisions of 6Li and 87Rb atoms when exposed to various common background gases found in ultra-high vacuum (UHV) environments, including H2, He, Ne, N2, Ar, Kr and Xe. Ultra-cold 6Li and 85,87Rb atoms are used as a sensitive probe of the background gas pressure, with the quantity ⟨σlossv⟩ essential for converting the observed loss rate due to background gas collisions into a pressure measurement.  Finally, we discuss the production of ultra-cold mixtures of 6Li and 85,87Rb atoms, and the progress towards investigating heteronuclear Feshbach resonances. The Feshbach resonances allow us to tune the interaction strength, which is an essential tool for investigating few and many-body physics in these systems. We discuss the particular example of the Efimov effect, which would be a natural topic of study following our investigating of the Feshbach resonance spectrum.  Event Location: Henn 318