Taming ultracold RbSr and Sr₂

Abstract

Ultracold molecules have recently attracted much attention because of their envisioned impact on both technology and fundamental science. The physics within them, i.e. their rich internal structure, and between them, i.e. long-range interactions, offer an increased complexity compared to atoms, while allowing for full experimental quantum control of the relevant degrees of freedom. A promising method of production consists of a first stage, whereby the component atoms are trapped and cooled to ultracold temperatures, and a second stage, whereby these are associated into dimers. In particular, the ability of cooling alkaline-earth (AE) elements, besides more traditional alkalis (A), has put production of AE-AE and A-AE molecules within experimental reach. Homonuclear ground-state AE-AE, because of their insensitivity to external electric and magnetic fields, have been proposed for metrology and precision measurements. In this work we investigate efficient production of Sr dimers starting from either an atomic Mott-insulator or Bose-Einstein condensate. Heteronuclear ground-state A-AE would allow for novel few-body and many-body physics experiments. In this thesis we investigate production schemes for RbSr dimers, which oweing to their large electric and magnetic dipole moments and heavy mass, are ideal candidates for the attainment of quantum degeneracy and subsequent experiments. We show our results from optical spectroscopy and combine them with thermal fluorescence data from our collaborators in Warsaw to derive the ground-state potential energy curve. Finally, we report on the experimental observation of magnetic Fano-Feshbach resonances between Rb and Sr and argue for their applicability to efficient molecule production