Understanding atom-ion collision dynamics is at the heart of the growing field of ultra-cold atom-ion physics. In our system, we overlap a ground-state cooled 88Sr+ ion with ultra-cold 87Rb atoms. We measure the ion’s energy distribution using narrow optical clock spectroscopy after few collisions and using Doppler re-cooling thermometry in steady-state. Despite the fact that both species start at μK temperatures, we observe the heating of the ion to mK temperatures after few collisions. We also observe a deviation in the energy distribution from Maxwell-Boltzmann characterized by an exponential tail to one with power-law tail described by Tsallis q-exponential function. These phenomena are explained by the intrinsic nature of the ion Paul trap which consist of oscillating electric fields. Despite the fact that our system is eventually driven out of the ultra-cold regime, we are capable of studying ultra-cold physics by limiting the interaction to the first collision.
In this talk I will review this work (https://arxiv.org/abs/1603.01810) and also new experiments involving in-elastic process such as spin-exchange, charge-exchange and quenching.