We have developed a novel experimental technique to study charge and energy flow processes in sub-electronvolt collisions between oppositely charged, internally cold, ions of atoms, molecules and clusters. Two ion beams are stored in separate rings of the cryogenic ion-beam storage facility DESIREE, and merged in a common straight section where a set of biased drift tubes is used to control the center-of-mass collision energy locally in fine steps. Here, we present measurements on mutual neutralization between Li${}^{+}$ and D${}^{-}$ where a time sensitive imaging-detector system is used to measure the three-dimensional distance between the neutral Li and D atoms as they reach the detector. This scheme allows for direct measurements of kinetic energy releases, and here it reveals separate populations of the $3s$ state and the $(3p+3d)$ states in neutral Li while the D atom is left in its ground state $1s$. The branching fraction of the $3s$ final state is measured to be $57.8\pm 0.7\%$ at a center-of-mass collision energy of $78\pm 13$ meV. The new technique paves the way for studies of charge-, energy- and mass-transfer reactions in single collisions involving molecular and cluster ions in well defined quantum states.

中文翻译：

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低温合并离子束实验：最终状态解析的Li +和D-互中和

我们已经开发出一种新颖的实验技术来研究带相反电荷的，内部冷的原子，分子和团簇离子之间的亚电子碰撞中的电荷和能量流动过程。两个离子束分别存储在低温离子束存储设备DESIREE的单独环中，并合并在一个公共的直线段中，在该直线段中，使用一组偏置的漂移管以精细的步骤局部控制质心碰撞能量。在这里，我们介绍了锂之间相互中和的度量${}^{+}$ 和D${}^{-}$其中使用时间敏感的成像探测器系统来测量中性Li和D原子到达探测器时的三维距离。该方案可以直接测量动能的释放，在这里它揭示了动能释放的单独种群。$3s$ 状态与 $（3p+3d）$ D原子保持其基态时处于中性Li状态 $\mathrm{1个}s$。的分支分数$3s$ 最终状态被测量为 $57.8\pm 0.7％$ 在质心碰撞能量为 $78\pm 13$影片 这项新技术为研究在明确定义的量子态下涉及分子和簇离子的单次碰撞中的电荷，能量和质量转移反应铺平了道路。