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Electron excitation and bombardment effect induced by polyatomic ions

多原子离子引起的电子激发和轰击效应

基本信息

批准号：
14550052
负责人：
KANEKO Toshiaki
金额：
$ 0.77万
依托单位：
Okayama University of Science
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14550052/
关键词：
cluster ion energy-loss dielectric function method secondary electron average charge carbon cluster stopping power carbon foil カイネティック放出電子励起

项目摘要

We studied the electronic energy-loss of swift polyatomic ions in solids and the secondary electron emission under their bombardment. First, we developed the self-consistent average charge theory for cluster ions. Our theory predicts the cluster charge average per ion is less than that of the isolated ion at an equivalent speed. The dependences on the number of constituent atoms, on the foil thickness, and on the spatial structure were found to be well explained. By taking into the coulomb explosion and the cluster average charge, we calculated the electronic energy loss of carbon cluster ions with the MeV/atom energies. In spite of the reduction of the average charge per ion, the energy loss per ion of the cluster is greater than that of the single ion at an equivalent speed(this is called the 'positive' cluster effect). In our treatment, the 'negative' cluster effect is also predicted for lower ion speeds. We found that the threshold speed in this cluster effect is located around two times Bohr velocity for the carbon clusters, and it does not so strongly depend on the foil thickness. Next, we investigated the secondary electron(SE) emission from carbon foil by the MeV/atom carbon clusters. The relative SE energy spectra per ion calculated on the basis of the three-step model showed the sublinear effect. This result is consistent with the recent experimental data by Kudo et al. The relative SE yield is also related with the cluster stopping power and with the cluster average charge. Finally we studied the multiple ionization process by the ionization probability in the 'energy transfer model'. The calculated cross sections agree with the data for rare gas atoms even for the incidence of swift highly charged ions, without any fitting parameters.

研究了多原子快离子在固体中的电子能量损失及其轰击下的二次电子发射。首先，我们发展了团簇离子的自洽平均电荷理论。我们的理论预测，在相同的速度下，每个离子的团簇电荷平均值小于孤立离子的电荷平均值。组成原子的数量上的依赖关系，箔的厚度上，并在空间结构上被发现被很好地解释。在考虑库仑爆炸和团簇平均电荷的情况下，用MeV/原子能量计算了碳团簇离子的电子能量损失。尽管每个离子的平均电荷减少，但在相同的速度下，团簇的每个离子的能量损失大于单个离子的能量损失（这被称为“正”团簇效应）。在我们的治疗中，“负”集群效应也预测较低的离子速度。我们发现，在这种集团效应的阈值速度位于约两倍玻尔速度的碳团簇，它并不那么强烈地依赖于箔的厚度。接下来，我们研究了MeV/atom碳团簇从碳箔的二次电子（SE）发射。在三步模型的基础上计算出的每个离子的相对SE能谱显示出次线性效应。这一结果与Kudo等人最近的实验数据相一致。相对SE产额还与团簇阻止本领和团簇平均电荷有关。最后利用能量转移模型中的电离几率研究了多次电离过程。计算的截面与稀有气体原子的数据一致，即使是快速高电荷离子的入射，没有任何拟合参数。