Wang Yan-Sen

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.

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.

Charge-exchange in cesium ions/atoms scattered or sputtered from metal surfaces

Abstract The charge states of Cs ions/atoms scattered from Cs/W(110) or sputtered from Cs/Al surfaces have been calculated as a function of the work function and the temperature of the surface in terms of the time-dependent Newns-Anderson quantum model with the intra-atomic Coulomb interaction. The calculated results are in good agreement with the experimental data. Furthermore, the probabilities of charge states of the moving Cs ions/atoms approaching and leaving the surface are demonstrated.

Configuration mixing of the level (23 537)o9/2 in Nd II deduced from the optical isotope shifts by collinear fast-ion-beam laser spectroscopy

The optical isotope shifts in the transition 4f4 5d 6 K9/2 -(23 537)9/2 0 (5702 A) of Nd II by collinear fast-ion-beam laser spectroscopy have been used to deduce for the first time that the mixing probabilities of the configurations 4f3 5d2 , 4f4 6p and 4f3 5d6s of the level (23 537)9/2 0 are 0.84, 0.15 and 0.01 respectively.

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.

Calculation of diffusion barriers for helium atom in metals

The diffusion barriers for the single helium atom in 3d transition metals are systematically studied by effective medium theory without any adjustable parameters. In the calculation, the relaxiation effects of lattice are taken into account. The comparison of our calculated results with the available experimental data and other theoretical values shows good agreement.

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.

Charge states of sputtered atoms/ions

The charge states of sputtered cesium and oxygen ions/atoms from metal surfaces have been discussed with the time-dependent Newns-Anderson model. The final charge state distribution has been calculated as a function of work function of the surfaces. The calculated results fit the experimental data well. Besides, the dependence of the final charge states of the sputtered oxygen particles on the surface temperature is also predicted.