The Theoretical Study For KLL-Dielectronic Recombination And Polarization Of X-Ray Emissions Of Highly Charged Ions

Dielectronic recombination(DR) is an important process in collision of electrons with highly charged ions. The DR process exists widely in hot astrophysical, laboratory and fusion plasmas where it strongly affects both the charge-state distribution and the x-ray spectrum. Accurate knowledge of DR cross sections is therefore needed for modeling of astrophysical and fusion plasmas. The x-ray radiations from the DR process can provide information on the directionality of the electron currents and the orientation of the magnetic-field lines, and anisotropy of the electron energy distributions in plasmas, and can also be used as a diagnostic tool. In this thesis, the KLL dielectronic recombination processes and linear polarization degree of emitted x-rays are investigated for some highly charged ions with few electrons in the framework of Multi-configuration Dirac-Fock(MCDF) method and the density matrix theory. The present theoretical results are compared with the existing experimental measurements of electron beam ion trap(EBIT), and the influence of Breit interaction on DR strength and x-ray polarization are well discussed. The main content of this thesis includes the following several aspects:In the first chapter, we introduce the physical picture of electron collision with highly charged ions, and review the background and research status of the dielectronic recombination process.In the second chapter, we briefly described the theoretical method, including the MCDF method and the density matrix theory, and the detailed calculations for of the DR dielectronic recombination strength, and the angular distributions and linear polarization degrees of x-ray emissions.In the third chapter, the KLL DR processes are systematically investigated for the highly charged H-like and He-like titanium ions. The energy levels and corresponding radiative and auger transition probabilities are calculated for all of KLL resonance double excited state, and the resonance strength, linear poarization degree and angular distribution of emitted x-ray lines are presented for each of individual DR resonance. Comparison is made between the present results and the experimental measurements in EBIT by O 'rourke et al for the differential cross sections at 90 o, a good agreement is obtained.In the fourth chapter, the KLL DR processes and the polarization of emitted x-rays are studied for the highly charged H-like to B-like barium ions. The resonance energies, resonance width, and corresponding radiative and auger transition rates are sysmatically calculated for all of individual KLL resonance state. In the calculations, the electron correlation effects, QED effects, and Breit interactions are well considered. We present the DR resonance strengths and linear polarization degrees for each of barium ions mentioned above, and analyze the influence of Breit interactions on them. Furtherly, we compare the present calculated DR spectrum of Ba55+-Ba51+ ions with EBIT experimental measurements by considering the distributions of different charged barium ions, good consistency is obtained.