Study of the surface of magnetic material with multi-electron cature process

为了实现该项目，必须获得一种能够提供低速高电荷离子和高光束质量的离子源。由于研究涉及磁性材料、绝缘体等的离子-固体相互作用只需要弱光束，我们建立了一个紧凑的电子束离子源（EBIS）型离子源。在电子束能量为1.8keV、氩气压力为1 × 10^<-9> Torr的离子源下，我们成功地获得了300eV/q的氩^<15+>束流。带有一对永磁体的维恩滤光器也被用作电荷分离器。多电子捕获过程非常有趣，因为它在捕获事件前后受到电子-电子相关的强烈影响。作为第一步，我们研究了ZnO+TiO绝缘子的库仑爆炸。由于Ar^<q+> (q=1.3,6,9)捕获多个电子，引起局部带电，导致靶原子间发生库仑爆炸。利用TOF技术对二次离子的电荷状态进行了识别。实验结果表明，多重电子捕获发生在一个相当局部的区域。在之前的工作中，我们研究了正电子- c_ <60>的相互作用。作为高q的延伸，我们已经开始研究慢速高电荷离子与C_<60>之间的相互作用，这将为我们提供关于电子捕获事件的时间和空间局域化程度的信息，以及/或在C_<60>内部的多重电子捕获过程中的电子-电子相关信息。如果应用一个粗略的类比，我们可以说，主要的兴趣是看C_<60>在爆炸时表现得像气球还是像肥皂泡。(想象一下，一个气球和一个漂浮在空中的肥皂泡开始爆炸。如果是气球，爆炸会立即扩散到气球表面，而如果是肥皂泡，爆炸只在局部发生，然后逐步扩散到气球表面。

To perform the project, it is essential to get an ion source which provides low-velocity highly-charged ions with high beam quality. As one needs just a weak beam in studying ion-solid interaction involying magnetic material, insulator, etc., we have built a compact EBIS (Electron Beam Ion Source) type ion souce. Operating the ion source with the electron beam energy of 1.8keV and Ar gas pressure of 1x10^<-9> Torr, we have succeeded to get 300eV/q Ar^<15+> beam. A Wien-filter with a pair of permanent magnets has also been built as a charge separaptor.Multiple electron capture process is very interesting because it is strongly affected by electron-electron correlation before and after the capture events. We have, as the first step, studied a Coulomb explosion of insulator (ZnO+TiO). The Coulomb explosion occurs among target atoms because multiple electron capture by Ar^<q+> (q=1.3,6,9) induce a local charge-up. The TOF technique is employed to identify the charge state of the secondary ion.The experimental results infur that multiple electron capture occurs from a rather localized area. In a previous work, we had studied positron-C_<60> interactions. As an extension to high q, we have started to investigate the interaction between slow highly-charged ion and C_<60>, which will provide us with information on the extent of time and space localization of electron capture events, and/or on electron-electron correlation inside C_<60> during multiple electron capture. If a crude analogy is applied, we may say that the major interest is to see whether C_<60> behaves like a balloon or like a soap bubble during explosion. (Imazine that a balloon and a soap bubble floating in the air now start explosion. In the case of a balloon, the explosion spreads over the balloon surface immediately, how-ever, in the case of a soap bubble, the explosion occurs locally and spreads over the surface step by step.)