Collision of cold ions stored in an electrostatic ion storage ring

在东京城市大学首次构建了以ln2冷却的静电离子存储环（TMU E-ring），并成功存储了亚稳离子和大分子离子等多种离子。与现有的E-rings、Aarhus的ELISA和KEK的ESRING相比，不同质量的各种离子同时存储，并且借助本研究开发的尺寸选择性光束处理技术，特定的离子被存储、喷射、聚束、脱束或加速。正如ELISA小组所证明的，E-ring是研究长寿命亚稳离子的合适装置，它可以在几毫秒到几秒钟内储存离子。本研究测量了双荷电CO_2的寿命。为了拟合所测得的衰减曲线，至少需要三个衰减分量。对于大分子离子，激光解吸源产生的富勒烯和卟啉阴离子储存在环内。研究了激光诱导卟啉阴离子的电子脱离，重点研究了延迟电子发射。中性产率的时间曲线不符合t-1依赖关系，而t-1依赖关系被广泛接受为内热离子的衰变曲线。这些结果表明，光激发阴离子的能量分布与从离子源中提取的“热”离子不同，对激发方式相当敏感。通过扫描激发波长，首次测量了气相阴离子的吸收光谱。

An electrostatic ion storage ring (TMU E-ring) was constructed in Tokyo Metropolitan University as a first LN2-cooled E-ring, and various ions including metastable ions and large molecular ions were successfully stored. In contrast to the existing E-rings, ELISA at Aarhus and ESRING at KEK, various ions with different masses were stored simultaneously, and by virtue of size-selective beam-handling techniques developed in the present study, specific ions were stored, ejected, bunched, de-bunched, or accelerated.As demonstrated by the ELISA group, E-ring is a suitable device for the study of long-life metastable ions it can store ions in several milliseconds to seconds. In the present study, lifetime of doubly charged CO_2 was measured. To fit the measured decay curve, at least three decay components were needed. Concerning large molecular ions, fullerene and porphyrin anions generated in a laser desorption source were stored in the ring. Laser-induced electron detachment of porphyrin anions was studied focusing attention onto delayed electron emission. Time profile of the neutral yield was not well fitted by t-1 dependence, which is widely accepted for the decay profile of internally hot ions. These results indicate that the energy distribution of the photo-excited anions would be different from "hot" ions extracted from the ion source, and quite sensitive to the way of excitation. By scanning excitation wavelength, absorption spectra of gas-phase anions were also measured for the first time.