Ding Xiao-Bin

Polarization and Angular Distribution of Lℓ X-Ray Following Inner-Shell 2p3/2 Photoionization of Magnesium-Like Ions

The inner-shell 2p3/2 photoionization and the subsequent decay of Mg-like Fe14+, Cd36+, W62+ and U80+ ions are studied theoretically within the multiconfiguration Dirac—Fock method and the density matrix theory. Special attention is paid to exploring the influence of the non-dipole terms which arise from the multipole expansion of the electron-photon interaction in the photoionization process. The results show that the non-dipole contribution to the total cross section, the magnetic sublevels cross section of the photoionization process, the degree of linear polarization and angular distribution of the subsequent characteristic x-ray radiation become more important with the increase of photons energy and atomic nuclear Z. Especially for the cross section and the degree of linear polarization, the non-dipole contribution arrives at 50% for U80+ at four time energy threshold units. However, for the angular distribution, the maximum contribution does not exceed 4%, even for U80+ ions.

Resonance Energies, Absorption Oscillator Strengths and Ionization Potentials for the Element Hassium (Z = 108)

On the basis of successfully predicting low-lying energy levels for the element fermium (Z = 100), we calculate the resonance energies, absorption oscillator strengths and the first ionization potential of the element hassium (Z = 108) by taking important relativistic and improved electron correlation effects into account using the multiconfiguration Dirac–Fock method. These calculations are carried out with the aim of assisting experimental investigations of hassium.

Shake-up Processes in the 3d Photoionization of Sr I and the Subsequent Auger Decay

The shake-up processes accompanied by 3d photoionization and subsequent Auger decay are studied using multi-configuration Dirac—Fock methods. General agreement is obtained with the experimental results for both the photoelectron and Auger electron spectra. The energy and relative intensity of the 5s→6s shake-up accompanied by the 3d photoionization process are identified quantitatively.

Photoionization of 1s Electron and Corresponding Shake-Up Process in Ground and Excited Lithium Atoms

The cross sections of the Is electron photoionization and corresponding shake-up processes for Li atoms in the ground state Is2 2s and excited states 1s2 2p, 1s2 3s, 1s2 3p and 1s2 3d are calculated using the multi-configuration Dirac-Fock method. The latest experimental photoelectron spectrum at hv = 100 eV [Cubaynes D et al. Phys. Rev. Lett. 99 (2007) 213004] has been reproduced by the present theoretical investigation excellently. The relative intensity of the shake-up satellites shows that the effects of correlation and relaxation become more important for the higher excited states of the lithium atom, which are explained very well by the spatial overlap of the initial and final state wavefunctions. In addition, strong dependence of the cross section on the atomic orbitals of the valence electrons are found, especially near the threshold.

Influence of plasma effect on the energy levels and transition probabilities of hydrogen-like ions

The effect of plasma screening has been investigated by incorporating the Debye potential into the framework of the relativistic Dirac-Fock method， and the GRASP92 code has been modified to perform the calculations. As an example, we have studied the plasma effecting on energy levels and transition probabilities of H-like ions embedded in dense and hot plasma. The following three important results have been obtained: （1） all energy levels are shifted away from their unscreened values toward the continuum, and the shift of energy increases as screening strength decreasing. Furthermore, for each eigenstate with given quantum numbers n and l, there is a finite value of λc （critical length） which corresponds a zero energy. （2） For a given transition, the oscillator strength and transition probability decrease with increase of the screening strength. （3）　The degenerate fine-structure levels with the same n, j but different l can be destroyed by the plasma screening effect, even without the consideration of the Lamb shift, which has received little attention in the past.

Excitation and decay dynamics of 1s2s inner-shell double-vacancy states of neon atoms

The photo-excitation and Auger decay processes of inner-shell double vacancy states 1s2s2p6(1,3S)3s3p of neutral neon atoms have been studied theoretically. Multi-configuration Dirac-Fock (MCDF) calculations have been carried out, with electron correlation effects taken into consideration. The relaxation of core and excited orbitals and configuration interaction are found to be crucial to creating the double vacancy states by single photo-absorption. The predominant decay paths for the double vacancy states turn out to be of the LLM Auger decay to 1s 2s22p53s(3p), KLL Auger decay to 1s22s2p43s3p, and KLM Auger decay to 1s22p63s(3p). They lead to further Auger decay, creating the neon ions of multiple charge states. For both double and single vacancy states the spectator type of Auger process is dominated in all the Auger decay processes. Theoretical Auger electron spectra are presented for further investigations, experimental and theoretical.