Chen Chong-Yang

Multiconfiguration Dirac-Hartree-Fock calculations for intercombination lines in silicon-like ions

This paper reports on multiconfiguration Dirac-Hartree-Fock calculations for intercombination lines in highly charged silicon-like ions. Results for wavelengths, fine structure, transition rates, branching ratios and lifetimes are reported and compared with other theories and experiments. A review of the experimental situation is presented, and deviations from expected smooth trends along the sequence are discussed.

Electron-impact ionization cross sections and rates for ions of neon

A distorted-wave Born exchange (DWBE) approximation was used to calculate the electron-impact ionization cross sections and rate coefficients for the ions of . The comparison of the calculated results with the experimental data and other theoretical calculations shows that the DWBE method is valid for all the ions of neon. The results of the calculations for cross sections were fitted by empirical formulae to meet the requirements of applications. A set of improved empirical formulae were developed for the fast and accurate calculations of rate coefficients from the fit parameters of cross sections.

KLn Dielectronic Recombination Process of B- Through He-like Cu Ions

The KLn dielectronic recombination processes of trapped highly charged B-like through He-like Cu ions are studied theoretically, and the theoretical results are used to analyse our previous experimental data at Heidelberg electron beam ion trap (EBIT). The theoretical resonant positions agree with the experimental resonant positions to a precision of 0.4%, in comparison with the resonant positions of those highest peaks between theory and experiment. The experimental spectra are then fitted using a formula with the theoretical resonant energies and strengths, the result shows good overall agreement between theory and experiment over a wide electron energy range. The distribution of highly charged states is obtained from the fitting parameters.

Photon angular distribution and polarization of radiative recombination

A systematic study is carried out on the angular distribution and polarization of photons emitted following radiative-recombination of bare and He-like ions of Ne, Ar, Ni and Mo with a unidirectional electron beam. In order to incorporate the screening effect due to inner-shell electrons, a distorted wave method is used. Scaling rules for polarization of the photon following radiative recombination to both bare and He-like ions are given for the incident energy regions up to six times the ionization threshold energy of the final state.

A Calculation of Direct Radiative Recombination Cross Sections and Rate Coefficients

We calculate direct radiative recombination cross sections and rate coefficients for Be-like O4+, Si10+ and Na-like Fe15+ using nonrelativistic dipole approximation. In order to incorporate the screening effect due to the inner-shell electrons in the calculation, we use the distorted wave method instead of pure Coulomb approximation with effective charge. The calculated cross sections and rate coefficients are in agreement with other theoretical calculations and the experimental data.

A Calculation of Electron Impact for the 3d5/2 → 2p3/2 Line Emission of Fe23+

By using the semi-relativistic distorted-wave Born exchange method, electron impact cross sections for the Fe23+ line emission 3d5/2 → 2p3/2 are calculated. The calculation involves line formation by direct electron-impact excitation, radiative cascade, resonant excitation, and dielectronic recombination satellites with captured electron in the n ≥ 5 levels. The results show a good agreement with the recent measurements.

Resonance enhanced electron impact excitation for P-like Cu XV*

Employing both the Dirac R-matrix and the relativistic distorted wave with independent process and isolated resonance approaches, we report resonance enhanced electron impact excitation data (specifically, effective collision strengths) among the lowest 41 levels from the n = 3 configurations of Cu XV. The results show that the latter approach can obtain resonance contributions reasonably well for most excitations of Cu XV, though a comparison between the two approaches shows that the close-coupling effects are truly significant for rather weak excitations, especially for two-electron excitations from the 3s3p4 to 3s23p23d configuration. Resonance contributions are significant (more than two orders of magnitude) for many excitations and dramatically influence the line intensity ratios associated with density diagnostics.

Calculation of photon angular distribution and polarization for radiative recombination for high-charged hydrogen-like ions

In this paper a systematic study is carried out on the angular distribution and polarization of photons emitted following radiative recombination of H-like ions by a non-relativistic dipole approximation. In order to incorporate the screening effect due to inner-shell electrons, a distorted wave approach is used. The dependences of the calculated angular distribution and polarization on the reduced energy and nuclear charge are fitted by the corresponding empirical formulas respectively.

Relativistic calculation of dielectronic recombination for He-like krypton

Dielectronic recombination (DR) cross sections and rate coefficients of He-like Kr are calculated employing the relativistic flexible atomic code, in which autoionization rates are calculated based on the relativistic distorted-wave approximation and the configuration interaction is considered. The Auger and total radiative rates of some strong resonances are listed and compared with the results from multiconfiguration Dirac–Fock and Hebrew University Lawrence Livermore Atomic Code methods. The n−3 scaling law is checked and used to extrapolate rate coefficients. We also show the variation of DR branching ratio with different DR resonances or atomic number Z. The effect of radiative cascades on DR cross sections are studied.

EFFECT OF CONFIGURATION INTERACTION ON EXCITATION AUTOIONIZATION CROSS SECTIONS

The effect of configuration interaction (CI) on the theoretical calculation of autoionization cross section for Li-like ions are studied in detail by employing the distorted wave Born exchange approximation. We consider the 1s22s → 1s2s2p and 1s22s → 1s2s3p transitions for C3+ and Al10+ ions. These two transitions account for the largest excitation autoionization cross section. It is found that the CI has a significant effect on the calculated results. The effect becomes larger with increasing atomic number.