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.

我们研究了固体中快速多原子离子的电子能量损失以及它们轰击下的二次电子发射。首先，我们发展了簇离子的自洽平均电荷理论。我们的理论预测每个离子的簇平均电荷小于同等速度下孤立离子的平均电荷。人们发现，对组成原子数量、箔厚度和空间结构的依赖性得到了很好的解释。通过考虑库仑爆炸和团簇平均电荷，我们用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，但簇中每个离子的能量损失大于同等速度下单个离子的能量损失（这称为“正”簇效应）。在我们的治疗中，还预测较低离子速度会产生“负”簇效应。我们发现，这种团簇效应的阈值速度约为碳团簇玻尔速度的两倍，并且它并不那么强烈地依赖于箔厚度。接下来，我们研究了 MeV/原子碳簇从碳箔发出的二次电子（SE）。基于三步模型计算的每个离子的相对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一致。相对 SE 产率还与簇停止本领和簇平均电荷有关。最后我们通过“能量转移模型”中的电离概率研究了多重电离过程。计算出的横截面与稀有气体原子的数据一致，即使对于快速高电荷离子的发生也是如此，无需任何拟合参数。