氢等离子体系中的电子过程及离子碰撞

【作者】 丁丁；

【导师】 屈世显；

【作者基本信息】 陕西师范大学 ， 声学， 2013， 博士

【摘要】 强磁场下的重粒子碰撞激发过程是重要的非弹性碰撞过程,但相关研究还几乎是空白。本文应用经典蒙特卡洛方法详细研究了不同强度的纵向和横向强磁场环境下,到不同主量子数n和磁量子数m的碰撞激发过程的态选择截面。同时用非微扰量子方法,得到了强磁场下靶原子的能级,并分析了其随磁场强度变化的原因。对于碰撞过程,发现由于磁场的引入导致到不同m态的激发截面有较大的分离,同时在较低入射能区的态选择截面变化行为与磁场方向有很大关系。这与能级变化及横向强磁场所特有的抗磁项的相互竞争有重要关系。通过对有关事例、径迹的分析,解释了这些变化形成的原因。也发现由于核的运动,沿磁场方向的轨道角动量并非绝对守恒,而有微小的变化。我们同样也应用经典蒙特卡洛方法详细研究了强磁场环境下He2++H(1s)的重粒子碰撞电离过程,得到了在不同强度的纵向和横向磁场下电离电子的一阶能量微分截面。发现它们不仅在数值上比未加磁场下的结果有明显的增加,而且随电离电子的能量变化不再是单调下降,而是呈现一定的峰值结构。通过对电离事例的分析,解释了这些变化形成的原因。其次,由于强磁场会导致碰撞电离的物理机制有很大变化,对此也分析并解释了磁场强度、方向及入射粒子能量等因素对电离机制的影响行为。本文做的另外的一个工作是通过非微扰求解薛定谔方程,研究了强磁场磁化的等离子体环境中的原子能级结构和辐射动力学过程。通过非微扰求解薛定谔方程,得到了在德拜等离子环境下的电子的本征值和本征函数。在较宽的磁场强度范围和等离子体屏蔽参数范围内,给出了氢原子基态以及低激发态的能级、辐射跃迁能量和振子强度等重要的原子参数,定量地描述了强磁场和等离子体屏蔽共同作用的综合效应。随着等离子体屏蔽效应的增强,Lyman线系会发生红移并降低谱线的发射强度。随着附加磁场强度的增强,对于n大于3的量子态,非微扰效应显著。同时本文还给出了跃迁几率,波长以及偶极强度随德拜屏蔽影响强弱和磁场强度大小的的变化趋势,并做出了相关解释。得到的结果有助于增进对极端环境下原子光谱结构的认识,在等离子体光谱诊断和天文光谱观测方面有一定的借鉴意义。另外,本文在强磁场和等离子体屏蔽同时存在的情况下,类氢离子精确的能级值基础上,采用经典蒙特卡洛方法对He2++H(1s)碰撞过程进行了分析。通过对所得的结果进行分析可知：对于碰撞电离总截面,在不同的德拜半径和磁场强度下的电离总截面与氢原子的能级值有很大的关系。当德拜半径越小,磁场强度越强时,氢原子的能级值越高,这时电子更容易被电离,即这时的电离截面就越大；电离电子能量的一阶微分截面,总的变化趋势是与电离总截面的变化趋势是一致的,但是微分截面还是有一些不同。对于造成这种变化的原因,在本文中也给出了相应的解释。更多还原

【Abstract】 Based on the excitation cross sections in collisions of H(1s) atoms with He2+obtained by the classical trajectory Monte Carlo method, the state-selective cross sections of excitation processes for different n and m, where n and m are the principle and magnetic quantum number respectively, are studied with the strong longitudinal and transverse magnetic fields applied. Meanwhile the precise energy levels for atom H in the strong magnetic fields are obtained by non-perturbative quantum method. It is found that there is some strong separation of the state-selective cross sections among different magnetic quantum states. Such behaviors are related to the variation of the energy levels and the diamagnetic terms induced by the applied magnetic fields. The diamagnetic terms in transverse magnetic fields results in the rapid increasing of the cross sections for the state of negative m at25keV/u, which is further indicated by the trajectory in this case. In some cases the decreasing of the total excitation cross sections is found due to the rising of the energy levels caused by the magnetic fields. The orbital angular momentum along the direction of the magnetic field is not conserved absolutely, which is found in the trajectories and agrees with our analysis. The first order differential cross sections for ionization have been calculated for different field strength of both transverse and parallel magnetic fields. It was found that the results have been increased obviously with the fields applied. Instead of monotonous decline, a peak appears for the differential cross sections with the fields applied. According to the analysis of trajectories, it is found that the ionization mechanisms have become quite different. In this paper, it is also interpreted the influence the strength and direction of the applied field including the incident energy on the ionization mechanisms.The other work is hydrogen atom imbedded in Debye plasmas with an external magnetic field, the combined effect on bound-bound transitions is investigated herein. The electron eigenenergies and wave functions are determined by non-perturbative solving the Schrodinger equation. Both transition frequencies and oscillator strengths are presented for a wide range of plasma screening parameters and external magnetic field strengths. With increasing the plasma screening, the shielding effects on the Lyman series are manifested in the decrease of its intensity and the red-shift of its frequency. After adding an external magnetic field, atomic energy levels undergo even stronger perturbation, as well as the line shapes become polarized. The non-perturbative effect is significant for the quantum states (n>3). Comparisons are made to other theoretical calculations with good agreement. The wave length,transition probability and the dipole strength of hydrogen atom with various values of Debye screening parameters and strength of magnetic field. We also give some interprets about these results The results reported here should be useful for the interpretation of spectral properties of H-like ions in laboratory and astrophysical Debye plasmas.Based on the hydrogen atom imbedded in Debye plasmas with an external magnetic field, the collision processes of H(ls) atoms with He2+is be discussed. The result of total cross section is effected by the atom structure. The first order differential cross sections for ionization and the difference of ionization mechanisms be found also be found. The tendency of the first order differential cross sections for ionization is agree with the result of total cross section.But the first order differential cross sections for ionization has some differential.In this paper,we also give the interprets.更多还原