Direct Observation of Atom-Ion Nonequilibrium Sympathetic Cooling.

摘要: Sympathetic cooling is the process of energy exchange between a system and colder bath. We investigate this fundamental in an atom-ion experiment where composed single ion trapped radio-frequency Paul trap prepared classical oscillatory motion with total $\ensuremath{\sim}200\text{ }\text{ }\mathrm{K}$, bath ultracold cloud atoms at $\ensuremath{\mu}\mathrm{K}$ temperature. directly observe sympathetic dynamics single-shot measurements during one to several collisions two distinct regimes. In one, predominantly cool very efficient momentum transfer leading only few collisions. other, can both heat due nonequilibrium presence trap's oscillating electric fields. While bulk our observations agree well molecular-dynamics simulation hard-sphere (Langevin) collisions, measurement scattering angle distribution reveals forward-scattering (glancing) which are beyond Langevin model. This work paves way for further collision studies using well-controlled system.