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A fully relativistic distorted-wave program is developed based on the Grasp92 and Ratip packages to calculate electron impact excitation (EIE) cross sections. As a first application of the program, the EIE cross sections of Be-like C2+ ions from the metastable 1s22s2p 3P to 1s22p2 3P excitation and the inner-shell excitations are calculated systematically. Meanwhile, the correlation effects of target states are discussed. It is found that the correlation effects play an important role in the low energy EIE cross sections. An excellent agreement is found when the results are compared with previous calculations and recent measurements.

Based on the Dirac–Fork–Slater method combined with the multichannel quantum defect theory, the recombination processes of electrons into bare uranium ions (U92+) are investigated in the relative energy range close to zero, and the x-ray spectrum emitted in the direct radiative recombination and cascades processes are simulated. Compared with the recent measurement, it is found that the rate enhancement comes from the additional populations on high Rydberg states. These additional populations may be produced by other recombination mechanisms, such as the external electric-magnetic effects and the many-body correlation effects, which still remains an open problem.

In the framework of multi-configuration Dirac–Fock theory, a detailed calculation is performed for the decay rates and the energies of the doubly excited 2s2 1S0 state of He-like ions, of which atomic number Z ranges from 6 to 92. The 2s2 1S0 – 1s2S1/2 Auger decay is predominant at low Z regime, whereas the 2s2 1S0 – 1s2p 1,3P1 two-electron one-photon transitions become quite important in moderate and high Z regimes. For heavy ions with Z≥72, the contribution of 2s2 1S0 – 1s2s3S1 M1 transition is significant. The Breit interaction considerably enhances the 2s2 1S0 – 1s2S1/2 Auger rate at high Z regime.

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.

Based on the multi-configuration Dirac–Fock method, theoretical calculations are carried out for the dielectronic recombination (DR) rate coefficients and the collision excitation rate coefficients of Sn10+ ions. It is found that the total DR rate coefficient has its maximum value between 10 eV and 100 eV and is greater than either the radiative recombination or three-body recombination rate coefficients (the number of free electrons per unit is 1021 cm3) for the case of Te > 1 eV. Therefore, DR can strongly influence the ionization balance of laser produced multi-charged tin ions. The related dielectronic satellite cannot be ignored at low temperature Te < 5 eV.

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.

The angular distribution and polarization of the x-ray photoemission of highly charged helium-like ions is studied following the K—LL dielectronic recombination of initially hydrogen-like ions. Calculation is carried out within the framework of the density matrix theory combined with the multiconfiguration Dirac—Fock approach. Attention is paid to magnetic sublevel alignment in the resonant intermediate state and to its nonuniform radiative decay processes. It is shown that the Breit interaction between the incident and target electrons plays a significant role for the alignment of the resonant state and thus causes a substantial change in the x-ray emission characteristic, when compared to the incorporation of only the (non-relativistic) Coulomb interaction. The most prominent difference in alignment parameter is found in the 2s2p1/2 J = 1 resonant state for a wide range of atomic numbers from 9 to 92. For this resonant state of helium-like ions, the Breit interaction becomes significant for ions with nuclear charge Z ~ 30 already.

The differential and integral cross sections for electron impact excitation of lithium from the ground state 1s22s to excited states 1s22p, 1s23l (l = s,p,d) and 1s24l (l = s,p,d,f) at incident energies ranging from 5 eV to 25 eV are calculated by using a full relativistic distorted wave method. The target state wavefunctions are calculated by using the Grasp92 code. The continuum orbitals are computed in the distorted-wave approximation, in which the direct and exchange potentials among all the electrons are included. A part of the cross sections are compared with the available experimental data and with the previous theoretical values. It is found that, for the integral cross sections, the present calculations are in good agreement with the time-independent distorted wave method calculation, for differential cross sections, our results agree with the experimental data very well.

Excitation energies and electron impact excitation strengths from the ground states of Ni-, Cu- and Zn-like Au ions are calculated. The collision strengths are computed by a 213-levels expansion for the Ni- like Au ion, 405-levels expansion for the Cu-like Au ion and 229-levels expansion for the Zn-like Au ion. Configuration interactions are taken into account for all levels included. The target state wavefunctions are calculated by using the Grasp92 code. The continuum orbits are computed in the distorted-wave approximation, in which the direct and exchange potentials among all the electrons are included. Excellent agreement is found when the results are compared with previous calculations and recent measurements.