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[en] Highlights: • Plasma environment effects on the energies and transition properties for the 3C and 3D lines of Ne-like Fe16+ ion are provided. • Two kinds of ion-sphere (IS) potentials are adopted to describe the plasma screening. • The present work should be of help in the modelling and diagnostic of fusion plasma. - Abstract: Investigations on the energies and radiative properties of the 2p53d 1P1 → 2p61S0 (3C line) and the 2p53d 3D1 → 2p61S0 (3D line) transitions of a highly charged ion embedded in the strong-coupling plasma are made, taking the Fe16+ ion as an example. Two kinds of ion-sphere (IS) potentials are adopted to describe the plasma screening. The multiconfiguration Dirac–Fock (MCDF) method is employed as well to describe the relativistic and electronic correlation effects in the above atomic system. The screening effects on the transition energies, oscillator strengths, and 3C/3D oscillator-strength ratios are estimated. Systematic trends are observed for all the properties under study with respect to increased temperature and electron density. Our results show that both the 3C and 3D energies decrease, yet the oscillator strength of the 3C (3D) line decreases (increases), as the strength of plasma increases (temperature increases and electron density decreases). The present results are compared with the available values in the literature.
[en] The polarization of x-ray line emission from highly charged ions undergoing collisions with an electron beam has been a topic of continuous fundamental interest for decades. The understanding of the processes is important not only to diagnose the electron distribution anisotropy in high temperature plasmas, but also to provide the information on both the incident electrons and the excitation dynamics. Recently, on the basis of the well-known GRASP92/K and RATIP packages, a new fully relativistic distorted wave program, named REIE06 has been developed by our group. In this composition, some selected applications of the program are shown. A special attention has been paid on influences of the higher order effects to the polarization properties of the subsequent photoemission following electron impact excitation process. We hope these works will be helpful for further understanding the contributions from the higher order effects and getting more accurate polarization data. (author)
[en] Plasma-screening effects on the 1s1/2→2l(l=s,p) and 1s1/2→3d3/2 electron-impact excitation of highly charged ions are investigated, together with their subsequent radiative decay. The analysis is performed based on the multi-configuration Dirac–Fock method and the fully relativistic distorted-wave method incorporating the Debye–Hückel potential. To explore the nature of the effects, calculations are carried out based on detailed analyses of the integrated total and magnetic sublevel cross sections, the alignment parameters, the linear polarizations, and the angular distribution of the X-ray photoemission, as well as on corresponding data calculated in various Debye lengths/environments, taking the 2p3/2→1s1/2 and 3d3/2→1s1/2 characteristic lines of H-like Fe25+ ion as an example. The present results are compared with experimental data and other theoretical predictions where available. (author)
[en] We investigate the 2p photoelectron spectra of sodium atoms with the initial state at a photon energy of 54 eV. The analysis is performed based on the multi-configuration Dirac–Fock method. Special attention is given to the influences of correlation and relativistic effects on the spectra structures. To explore the nature and importance of such influences, calculations were performed based on detailed analyses of the thresholds, relative intensities and corresponding data calculated in the nonrelativistic limit. (paper)
[en] Within the framework of the Hartree-Fock method and the irreducible tensor theory, we have proposed an analytic formula for calculating the nonrelativistic energies of many-electron atoms. The relativistic mass, the one- and two-body Darwin, the spin-spin contact interaction, and the orbit-orbit interaction corrections to the energies are considered to make the results more precise. The angular interactions and spin sums involved in the formula are worked out explicitly using the irreducible theory. A program based on the variational method is developed to calculate the wave functions and atomic structure properties. The energies of the 1sns 1,3S (n = 1-4) and 1snp 1,3P (n = 2-4) states of the exemplary ions Ar16+, Fe24+, and Kr34+ in both Debye plasma and quantum plasma environments are given. Moreover, we analyzed the evolution of plasma screening parameters and provided some rules for practical and rapid evaluation in plasma applications. (author)
[en] Developing high-quality X-ray source to diagnose shock wave and changing the material and structure features of the target were presented to enhance its absorbability to ultra-intense laser energy. Experiments were carried out on the XingGuang-III Ti: sapphire laser facility (2.1– 6 J, 30 fs) at Laser Fusion Research Center, China Academy of Engineering Physics. The minimum intensity was 1.6 × 1018 W/cm2 on a nano-foam Cu target with the thickness of 100 µm, the porosity of 70% and the density ratio of 30% solids of Cu. The emission of Kα X-rays from the target was measured using a single-photon counting CCD device. This nano-foam target had generated a Kα peak photon rate of 2.9 × 108 photons sr−1 s−1 and the maximum conversion efficiency (CE) value was 0.0084%. The average CE of the nano-foam Cu was 1.8 times greater than that of foil Cu target. The minimum spot size of the X-ray source was measured to be about 40 µm at full width at half maximum, smaller than 47–86 µm of the foil Cu target using 0.1-mm thick knife-edge method. The nano-foam structure showed the potential of enhancing the CE of the femtosecond laser for X-ray conversion.
[en] In this work, the triple differential cross section for electron impact ionization of helium in the special geometry of coplanar high incident energies large energy loss and close to minimum momentum transfer are calculated by use of the BBK and modified BBK model after the shield effect of the residual electron is considered. Then, the influences of the effective shield of residual electron on the triple differential cross sections and the physical nature of these effects are discussed in detail. (authors)
[en] Electron impact excitation cross sections from the ground state and the lowest metastable state 5p56s J = 2 to the excited states of the 5p57p configuration of xenon are calculated systematically using the fully relativistic distorted wave method. Special attention is paid to the configuration interaction effects in the wave-function expansion of target states. The results are in good agreement with the recent experimental data by Jung et al. [Phys. Rev. A 80 (2009) 062708] over the measured energy range. These accurate theoretical results can be used in the modeling and diagnosis of plasmas containing xenon. (authors)