1School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049 2State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, and Collaborative Innovation Center of Quantum Matter, Beijing 100084 3Department of Physics, Capital Normal University, Beijing 100037
Abstract：An ion–neutral hybrid trap is built to study low-energy ion–atom collisions. The ion–neutral hybrid trap is combined with two spatially concentric traps: a linear Paul trap for the ionic species and a magneto-optical trap (MOT) for the neutral species. The total ion–atom collision rate coefficient $k_{\rm ia}$ between$^{87}$Rb atoms and optically dark $^{87}$Rb$^+$ ions is measured by monitoring the reduction of the steady-state MOT atoms by sequentially introducing various mechanisms, namely photoionization and ion–atom collisions. In contrast to other experiments, a concise experimental procedure is devised to obtain the loss rates of the MOT atoms due to photoionization and ion–atom collisions in one experimental cycle, and then the collision rate $k_{\rm ia}$ of cold $^{87}$Rb atoms with $^{87}$Rb$^+$ ions is deduced to $0.94(\pm0.24)\times10^{-13}$ m$^3$/s with $T_{\rm i}=3770(\pm100)$ K measured by the time of flight of the ion signal. The measurements show good agreement with the collision rate derived from the Langevin model.
2017, Vol. 34 
