Wang Jian-Guo

Positron-Impact Excitation of Hydrogen Atoms in Debye Plasmas

The positron-impact excitation of hydrogen atoms embedded in plasma environments is investigated using the close-coupling approximation from the low to intermediate energy region without including any positronium formation channel, and the excitation cross sections for 1s → 2s, 1s → 2p and 2s → 2p processes are calculated in a wide Debye parameter range. The screening interactions, described by the Debye–Huckel model, decrease the coupling matrix elements, resulting in the reduction of the excitation cross sections from a few percent to one magnitude of ten. This will alter remarkably the spectroscopy of hydrogen in intensity and position, which should be considered in the simulation and diagnostics under some specific plasma conditions.

Relativistic Distorted-Wave Calculations of Electron Impact Excitation Cross Sections of Be-Like C2+ Ions

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.

Calculations of Photo-Ionization Cross Sections for Lithium Atoms

Photo-ionization cross sections for the ground and the n ≤ 5 excited states of lithium atoms are calculated in the photoelectron energy ranging from threshold to 0.5 Rydberg. The wavefunctions for both the bound and continuum states are obtained by solving the Schrodinger equation numerically in a symplectic scheme. Our results are in excellent agreement with the recent experimental measurements and in harmony with other theoretical calculations.

Atomic Structures and Radiative Properties of He-like Ions in Debye Plasmas

A detailed investigation of plasma screening effects on atomic structure and transition properties are presented for He-like ions embedded in dense plasma environment. Multi-configuration Dirac-Fock calculations were carried out for these ions by considering a Debye-Huckel potential. A large-scale relativistic configuration-interaction method is adopted to calculate transition energies and transition probabilities and to allow for a systematic improvement of the calculations. Comparison of the presently calculated results with others, when available, is made.

Simulation of Hydrogen Emission Spectrum in Debye Plasmas

We investigate the screening effects on the spectrum of spontaneous radiation and radiative recombination to the 1s, 2s and 2p states of hydrogen with total atom density N = 1.7 × 1019 cm−3 and electron temperatures 1eV, 2eV and 5eV under the local thermodynamic equilibrium (LTE) model. The needed atomic energy levels, the radiative transition probabilities and radiative recombination cross sections are calculated by solving the Schrodinger equation numerically incorporating the Debye—Huckel model in plasmas. The plasma emission spectrum is simulated for the first time by using the screened atomic parameters. The red shift and the cutoff of Rydberg spectra are observed and it is also found that the 2 eV electron temperature case has the strongest screening effects and the emission spectra to the 2s and 2p states are more likely affected by screening effects than that of the 1s state.

Resonant charge transfer in slow Li+−Li(2s) collisions*

The resonant charge transfer process for Li+–Li(2s) collision is investigated by the quantum-mechanical molecular orbital close-coupling(QMOCC) method and the two-center atomic-orbital close-coupling(AOCC) method in an energy range of 1.0 e V/u–104e V/u. Accurate molecular structure data and charge transfer cross sections are given. Both the allelectron model(AEM) and one-electron model(OEM) are used in the QMOCC calculations, and the discrepancies between the two models are analyzed. The OEM calculation can also give a reliable prediction of the cross sections for energies below 1 ke V/u.

Fast-electron-impact ionization process by 3p of hydrogen-like ions in Debye plasmas*

The plasma screening of fast-electron-impact-ionization by excited state (3p) of Hydrogen-like ions was investigated in the first Born approximation with a plasma screening length δ varying from 1000a0 to 10a0. The generalized oscillator strength densities showed dramatic changes: some accessional minima occurred along with a remarkable enhancement in certain continuum-energy domains. The double-differential cross sections exhibit not only the same structures as the Bethe surface for moderate and large momentum transfers, but also a broadened enhancement for small momentum transfers. The single-differential cross sections exhibit a near-zero-energy-enhancement and prodigious multiple-shape resonances, depending on the continuum energy and the plasma screening length. These features are analogous to those of the photo-ionization cross section. These findings, for both types of cross section, can be explained by processes associated with continuum electrons, as long as the potential has a short-range character.

Calculation of the High-n Dielectronic Satellites of Kα Resonance Lines for Heliumlike Iron

A simplified relativistic configuration interaction method is used to study the dielectronic satellite transition processes, in which the whole high-n dielectronic satellite transition processes can be treated conveniently in the frame of quantum defect theory. The theoretical results for heliumlike iron are in good agreement with the experimental measurements.

Theoretical Calculation of Dielectronic-Recombination Cross Section for Hydrogen-Like Argon

Dielectronic-recombination cross sections of hydrogen-like argon are calculated conveniently by our simplified relativistic configuration-interaction method. The results for the KLL, KLM, KLN, and KLO resonances are in good agreement with experimental measurement within a few percent. Our methods can provide various dielectronic-recombination rates which can satisfy the need for relevant applications.

CTMC Investigation of Capture and Ionization Processes in P+H(1s) Collisions in Strong Transverse Magnetic Fields

The collision processes of proton with H(1s) atoms, which is embedded in strong transverse magnetic fields perpendicular to the initial velocity of the projectile, are studied with the classical trajectory Monte Carlo method in the energy range 25 keV/u–2000 keV/u and B ~ 104 T. It is found that the charge exchange cross section is decreased while the ionization cross section is increased significantly. The physics of magnetic field effects is analyzed by the time evolution of electron energy and trajectories, and it is found that these effects are induced by the diamagnetic term in the interaction, continuum electron trapping in the target regions and the Lorentz force. The velocity distributions of the ionized electrons, significantly influenced by the applied fields, are also presented.