【作者】 陈林；

【导师】 Vladimir Esaulov； 陈熙萌；

【作者基本信息】 兰州大学 ， 粒子物理与原子核物理， 2009， 博士

【摘要】 目前的实验工作主要包括两部分:一是在巴黎的LCAM实验室,完成了在掠射条件下离子-表面散射的能损的测量和大角度散射的条件下电荷转移的研究;二是在兰州大学完成了离子-原子碰撞的电荷转移的研究。本论文具体包括以下几部分:在第一章描述了离子-表面/原子相互作用的理论模型和相关概念。在第二章描述了本论文使用的实验仪器和技术。在第三和第四章,完成了1-4keV H⁺,He⁺和F^-离子在金表面散射的表面沟道和能损的研究。实验上发现能损依赖于表面的方位角的改变,同时在能谱图上观测到多峰结构。考虑了表面不均匀电子气的离子轨迹和相关能损谱的模拟得出多峰结构源于不同的轨迹类型。能损的计算和实验结果吻合很好。在第五章描述了Li⁺离子在Au（110）和Ag/Au（111）表面散射的电荷转移。实验上发现中性化份额对入射能量,出射角度,以及方位角均有依赖。其次在高功函表面如此有效的中性化是和传统的共振电荷转移模型相矛盾的。因此根据最近的理论研究成果,修正了传统的共振电荷转移模型,并给出了和实验结果大致相符的计算结果。我们用STM研究了Au（111）基底上生长超薄Ag膜,同时利用低能Li⁺离子背散射研究了电荷转移过程。入射离子中性化份额随入射能或出射能的增大而单调的减小,且并没有得到像人们预期的由于超薄膜Ag和基底Ag电子结构,能带结构的差异而引起中性化份额的不同。相比传统的jellium模型,改进的模型计算的结果和实验符合的很好。在第六章介绍了MeV C^q+离子和Ar靶碰撞的电荷转移的研究,给出了入射离子丢一个电子情况下的靶电离截面比的标度,研究发现入射离子丢（俘获）一个电子的情况的靶电离截面比或靶多电离与单俘获截面比均强烈依赖于入射离子的电荷态,而且随入射能的变化,各个反应道的变化激烈。实验上还观测到入射离子丢一个电子的情况下的靶多电离与纯单电离截面比随入射能量有振荡结构。在第七章我们还修改了过垒模型来处理多电荷态离子和氢原子和氦原子靶在中能区碰撞情况下的俘获和电离截面。这是一种非常简单的快速估算截面的方法,具有解析的表达式,容易理解物理实质,关键是能够给出正确的截面值。更多还原

【Abstract】 This dissertation is aimed at investigation of electronic energy loss and charge transfer process in particle - surface scattering performed in LCAM,Pads,and studies of charge transfer process in ion-atom collisions performed in Lanzhou University, Lanzhou.The present dissertation is arranged as follows:The concepts and theoretical model of ion - surface/atom interaction are presented in chapter 1.The main apparatus used in this work is presented in chapter 2.In chapters 3 and 4,we present the results of an experimental study of surface channeling and stopping of hydrogen,helium and fluorine ions in grazing scattering on Au surfaces at ion energies between 1 keV and 4 keV.Energy loss depending on different azimuthal orientations has been analyzed,and multi-peak structures in the energy spectra are observed and attributed to different trajectory classes.The, trajectory simulation involving electronic corrugation of the surface has been performed by J.Valdes and the simulated results are in good agreement with the experimental data.Charge transfer process of Li⁺ ions scattered off the clean Au（110） surface and Ag ultra-thin layer supported on Au（111） is presented in chapter 5.Neutral fraction of Li⁺ ions scattering off the clean Au（110） surface has been measured for different parameters（incident energies,exit angles and azimuthal orientations）.Highly efficient neutralization on noble metals with high work functions contradicts our traditional resonant charge transfer（RCT） mechanism.Modified RCT involving new, neutralization processes occurring at a much short internuclear distance has been performed and compared with our data.The growth of Ultra-thin Ag film on Au（111） was studied by STM,and neutral fraction of Li⁺ ions scattering off an ultra-thin Ag film supported on Au（110） has been performed.The neutral fraction decreases monotonically with the increase of the incident energies or exit energies and shows no difference from the Ag bulk.The model calculation shows a better agreement with the experimental data compared with the results based on the conventional jellium model.The charge transfer of MeV C^q+ in collision with Ar has been studied and presented in chapter 6.We get empirical scaling laws for the ratios of n-fold ionization corresponding to single electron loss by the projectile.It is observed that the ratios of n-fold ionization associated with single electron loss,the ratios of multi-ionization associated with single electron loss to pure single electron ionization and the ratios of multi-ionization associated with single electron capture to pure single electron capture are all dependent strongly on the charge states of the projectile and vary significantly in different reaction channels with the increasing impact energy in the present experiment.The ratios of multi-ionization associated with single loss to pure single ionization present an interesting oscillatory structure.Finally,modified theoretical model of over-barrier model was developed and used to treat charge transfer of multi-charged ions in collisions with the H and He target atoms,as shown in chapter 7.It is very simple for experimental physicists to estimate the cross section quickly.更多还原