【作者】 刘义保；

【导师】 尚仁成；

【作者基本信息】 清华大学 ， 物理学， 2005， 博士

【摘要】 电子与原子碰撞研究在物理学领域仍然非常活跃而且发展很快。传统的电子原子碰撞实验,主要是通过碰撞截面测量和计算来获取碰撞过程的信息,通过光谱、能谱或动量谱来分析靶结构信息。随着电子—光子符合散射实验技术和超级弹性散射实验技术不断提高以及计算机功能的迅速发展,电子原子散射激发完备性可观测量的量子理论和实验测量已成为非常有趣和有意义的课题。 所谓电子原子散射激发的完备性可观测量,就是指通过磁量子级上的散射振幅构造出来的一组最优化参量,这组参量可以描述散射受激态结构和散射激发动力学过程,并且是实验上可以测量的。 本文以碱金属原子作为电子散射激发的靶原子,根据量子散射理论和密度矩阵理论,利用态多极描述受激靶原子集,通过态多极和受激态退激偶极辐射光子的Stokes参数,建立磁量子级上的散射振幅和可观测量之间的关联,使用非相对论的扭曲波玻恩近似和间接相对论的扭曲波玻恩近似,计算了中低能电子与碱金属原子散射激发S→P跃迁的可观测量,即传统的微分散射截面和描述受激态的取向参数、排列角和线性极化度以及描述散射前后自旋变化的STU参数。 我们用非相对论的扭曲波玻恩近似研究了不同入射能下,完备性可观测量散射角分布的变化,得出了小角度散射下受激态取向参数和排列角明显的变化规律,部分计算结果与已有的实验结果符合较好,部分计算结果有待于实验的检验;从STU参数的计算结果,我们发现电子与碱金属原子散射激发从S态跃迁到P态的过程中,自旋交换效应不仅与入射能而且与散射角有关,低能入射电子的自旋交换效应比较明显。 我们还探索了用多组态Dirac-Fock方法描述重的碱金属原子波函数,而用薛定谔方诚描述连续电子,采用这样一种间接相对论扭曲波玻恩近,通过分析散射激发的完备性可观测量,研究电子与铷原子散射激发中的相对论效应,与最新的电子与铷原子散射激发实验结果比较,优于非相对论的计算,并获得了传统散射截面分辨不出来的散射过程的信息,取得一定的成果更多还原

【Abstract】 The study of electronic and atomic collision processes continues to be a very active and rapidly developing field of physics. The traditional object of electronic and atomic collision studies is a total or differential cross section. People analyse the structure information of target atom through the spectrum, the energy spectrum or the momentum spectrum. With the rapid developing of the computer power and the technology of scattering experiment, the quantum theory and experiment measurement of perfect observable quantities in electron-atom inelastic scattering are become the very interesting and meaningful subject.The so-called perfect observable quantities in electron-atom inelastic scattering are a set of optimal parameters which are based on the quantum scattering theory and are structured by the scattering amplitudes on the magnetic quantum sublevel, and these observable quantities can be measured by experiments and can describe the information of excited atom state and the dynamics of scattering.In this paper, we choose the alkali atoms as targets. According to the quantum scattering theory and density matrix theory, we use the state multipoles to describe the excited taget atom assemble, and set up the correlations between the scattering amplitudes of magnetics quantum sublevel and observable quantities by state multipoles and the Stokes parameters of radiation re-excited from the excited state. We use two types of distorted wave Born methods to calculate the alkali atom scattering matrix from S state to P state excited by electrons at low and moderate incident energy, i.e, non-relativity distorted wave Born approach (DWBA) and indirect-relarivity distorted wave Born approach (IR-DWBA). Then, we calculate the obervalbe quantities through the angular momentum theory and couple technology. The perfect observable quantities studied in this paper, are the orientation parameter, alignment angle and linear polarization degree which describle the excited atom state and the STU parameters which describe the spin changes before and after scattering.In DWBA, we calculate the scattering angle distribution of observable quantities of excited atom from S state to P state scattered by electron with sodium and potassium at different incident energies. The orientation parameter and aligment angles change regularly to the scattering angles and incident energies.The calculated results are partially agreement with reported experiment measurements, and some calculations need to be tested by experiments. From the calculations of STU parameters, we conclude that spin exchange effect is relative not only to the incident energy but also to the scattering angle. The spin exchange effect of electron is significant in the electron scattering with alkalli atoms at the low incident energy.We have explored to use the multi-configuration Dirac-Fock method (MCDF) to describe the wavefunction of alkali atoms, and use the Schrodinger equation to describe the continued electrons. In such IR-DWBA, we study the relativity effects in the scattering of electron excitedt with alkali-atom, and compare with the results of DWBA and measurements. We find that the results of IR-DWBA is prior to the calculations of DWBA when we treat with the DCS and the observable quantities of electron scattering with rubidium at 20 eV incident energy.更多还原