Trapped ions in an ultracold gas Buffer gas cooling and chemical reactions

This thesis documents our recent progress in researching cold interactions in a hybrid system of a trapped Yb⁺ ion and a cloud of ultracold ⁶Li atoms. The major areas of focus are buffer gas cooling, recent experimental upgrades and cold chemical reactions.
In particular, I numerically investigate how the parameters of our ion trap can be tuned to optimize buffer gas cooling and reach lower atom-ion collision energies. We predict a lower limit on the collision energy in our experiment of 0.6× the s-wave limit, corresponding to an average ion energy of 0.92 motional quanta.
On the experimental side, I describe a new optical ‘dimple’ potential that allows us to increase the density of our atom cloud as well as the expected enhancement in collision rates resulting from this density increase. This will be beneficial for facilitating more frequent chemical reactions and faster buffer gas cooling.
Finally, I present observations of collisions between the Yb⁺ ion and weakly-bound Li₂ dimers in the atom cloud, resulting in the formation of a LiYb⁺ molecular ion. I detail our investigation into the relationship between the concentration of dimers in our setup and the molecular ion formation rate, describing the theoretical models used to explain our experimental observations. I then apply these models, combined with our newly-characterized dimple trap, to make predictions for similar investigations in the future.