Theoretical Study On Electron-impact Excitation And Dielectronic Recombination Processes Of Highly Charged Fe And Si Ions

Electron with highly charged ions collision are important processes in plasmas environments such as astrophysical and laboratory.High precision atom data such as cross sections,collision strengths,resonant strengths,degrees of linear polarization and rate coefficients are very important for the simulation and diagnoses of various plasmas.In recent years,depend on the development of EBIT and CSR experimental devices,a series of important evolve have been obtained in the research of electron with highly charged ions collision processes.In this thesis,theoretical study are made electron-impact excitation（EIE）,resonant electron-ion captured（REC）and radiative decay processes of Fe²⁰⁺-Fe²¹⁺ions by using the flexible atomic code（FAC）.In additions,the EIE and DR rate coefficients of H-like to Be-like silicon ions were systematically calculated.The following work was carried out in detail:Firstly,the total and magnetic cross sections for EIE of C-like Fe²⁰⁺ion from the ground state(1s²2s²2p^{2 3}P₀)to the K-shell excited states（1s2s²2p³）_J=0,1,2=0,1,2 have been calculated.The detailed cross section depending on incident electron energy from 1-6threshold are presented,it reviews that single electron excitation are dominant in the most cases,however,the cross section of double electron excitation for[(1s2s²2p_1/2)¹(2p²_3/2)₁]₁ state surpass that of[(1s2s²2p²_1/2)¹2p_3/2]₂ from single electron excitation in higher energy region（E≥1.7thresolds）due to strong configuration mixing between[(1s2s²2p_1/2)¹(2p²_3/2)₁]₁ and[(1s2s²2p²_1/2)¹2p_3/2]₁.As a comparison,we also calculated the cross section of REC for B-like Fe²¹⁺ions forming the same excitation states as the Fe²⁰⁺EIE process.It is found that the REC process cross section is greater than EIE cross section.At the same time,degrees of linear polarization of x-ray emission from the same autoionizing intermediate states by EIE and REC processes are calculated and compared for the several stronger 2p→1s transitions.Significant differences are found between the polarizations of radiative x-rays following EIE and REC processes,that can be employed in diagnosing the formation mechanism of corresponding x-ray lines.Secondly,the rate coefficients of dielectronic recombination,direct and resonance electron-impact excitation were systematically calculated for Si¹³⁺-Si¹⁰⁺ions.We compared with the DR experimental results measured at Stockholm university electron beam ion trap of Si¹³⁺and Si¹²⁺ions.It is found that the present results agree excellently with the experimental values.The synthesized DR and EIE rate coefficients of highly charged Si¹³⁺-Si¹⁰⁺silicon ions were presented,it agreed with the experimental results,except for the values around the electron energy1.85keV a slight difference were existed between the theoretical and experimental results.