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Electron capture and excitation processes in H+-H collisions imbedded in warm dense quantum plasmas are studied by the two-center atomic orbital close-coupling (TC-AOCC) method in the energy range 1-200 keV. The screened potential which is used to describe the interaction between charged particles incorporates the quantum electron degeneracy, exchange-correlation and finite-temperature gradient correlation effects. The total and state-selective electron capture and excitation cross-sections for this collision system with this potential are calculated in a wide range of plasma densities and temperatures. It is demonstrated that the screening of Coulomb interactions affects the collision dynamics and the magnitude and energy behavior of the excitation and electron capture cross-sections. The results at very low and high temperatures are also compared with those obtained for zero-temperature quantum plasmas and Debye plasmas, respectively. [ABSTRACT FROM AUTHOR]

We simulate the evolution of ultracold neutral plasmas using molecular dynamics calculations with open boundary conditions. The calculations use 6000 ions and 6000 electrons, respectively, with a quasi-real ion-electron mass ratio of mi=me = 1000. The simulated plasmas have both Gaussian and ordered initial distributions. While disorder-induced heating is absent in the initially ordered distributions, the ions are heated significantly by electron-ion collisions. We show that the value of the strong coupling parameter typically falls below 10 for realistic plasma densities. [ABSTRACT FROM AUTHOR]

Plasma effects on the high-energy electron-impact ionization process from 2p orbital of Hydrogen-like ions embedded in weakly coupled plasmas are investigated in the first Born approximation. The plasma screening of the Coulomb interaction between charged particles is represented by the Debye Hückel model. The screening of Coulomb interactions decreases the ionization energies and varies the wave functions for not only the bound orbital but also the continuum; the number of the summation for the angular-momentum states in the generalized oscillator strength densities is reduced with the plasma screening stronger when the ratio of [variant_greek_epsilon]/I2p (I2p is the ionization energy of 2p state and [variant_greek_epsilon] is the energy of the continuum electron) is kept, and then the contribution from the lower-angular-momentum states dominates the generalized oscillator strength densities, so the threshold phenomenon in the generalized oscillator strength densities and the double differential cross sections are remarkable: The accessional minima, the outstanding enhancement, and the resonance peaks emerge a certain energy region, whose energy position and width are related to the vicinity between δ and the critical value δnlc, corresponding to the special plasma condition when the bound state |nl just enters the continuum; the multiple virtual-state enhancement and the multiple shape resonances in a certain energy domain also appear in the single differential cross section whenever the plasma screening parameter passes through a critical value δnlc, which is similar to the photo-ionization process but different from it, where the dipole transition only happens, but multi-pole transition will occur in the electron-impact ionization process, so its multiple virtual-state enhancements and the multiple shape resonances appear more frequently than the photo-ionization process. [ABSTRACT FROM AUTHOR]

The intensities of charge exchange recombination spectroscopy (CXRS) of α particles colliding with the hydrogen atoms in the neutral beam injection (NBI) are calculated by solving the rate equations including electron collision processes in the quasi-static state approximation. The effects of electron collision processes on the CXRS signals for He+(n=4→3) at λ=468.6nm in various plasma conditions are discussed, and it is found that these effects can increase the CXRS signals by 50% for electron density ne≥1015cm-3. However, their importance decreases with the increasing of NBI energy. For the short pulse of NBI, the influences of electron collision processes can be neglected for ne≤1014cm-3. Furthermore, the spectra of He+(n→n') are present for the plasma conditions of HT-7 tokamak. [ABSTRACT FROM AUTHOR]

The plasma screening effect on electron-impact excitation is studied by using the relativistic distorted-wave description and exemplified by the excitation of Ti21+ ion. The total and differential cross sections for the 1 s–2 s and 1 s–2 p excitations are calculated in the energy range from threshold to 5 times threshold energy, and the magnetic sublevel cross sections are also given. Comparison of present calculations with other results, when available, is made. [ABSTRACT FROM AUTHOR]

The photoionization cross sections in the photoelectron energy below 2 Ry are calculated for the ground and n≤4 excited states of Li embedded in plasma environments and the radiative-recombination (RR) rate coefficients for Li+ were presented for temperature T=100–32 000 K in a wide range of plasma parameters. The plasma screening interaction is described by the Debye–Hückel model and the energy levels and wave functions including both the bound and continuum states are calculated by solving the Schrödinger equation numerically in a symplectic integration scheme. The screening of Coulomb interactions remarkably changes the photoionization cross sections near the ionization threshold, and especially for the ns states, the Cooper minimum is uncovered and shifted to the higher energy as the screening interaction increases. The RR rate coefficients at low temperature have a complex variation on the Debye lengths; whereas at higher temperature the RR rate coefficients decrease with the increasing of screening effects. Comparison of present results with those of other authors when available is made. [ABSTRACT FROM AUTHOR]

Plasma screening effects on the high-energy electron-impact excitation of hydrogenlike ions are investigated under the first Born approximation. The screening interactions are described by the Debye–Hückel model, and the wave functions are calculated numerically in a symplectic scheme. The generalized oscillator strengths (GOS) for transitions between the principal quantum number n≲3 bound states are presented, and as an example, the scaled differential cross sections and total cross sections for 1s→2s and 2p and 2s→2p transitions are also given. It is found that the plasma screening interactions reduce the GOS for transitions between the states with different n and increase the GOS between the states with same n. The differential and total cross sections are decreased as the screening interactions increase. [ABSTRACT FROM AUTHOR]

The processes of charge exchange and ionization in collisions of ground state hydrogen atom with fully stripped ions in a weakly coupled plasma are studied by the classical trajectory Monte Carlo method in the collision energy range 10–900 keV/amu. The interparticle interactions are described by the Debye-Hückel model with inclusion of dynamical effects associated with the projectile velocity. The microcanonical distribution of initial state electronic coordinates and momenta has been determined by inclusion of plasma screening effects. The cross section dependencies on plasma parameters and ion charge and velocity are investigated. It is shown that plasma effects on charge exchange and ionization cross sections are significant and particularly pronounced at low collision velocities. The results of systematic cross section calculations for different values of Debye screening length (in the range 1–50a0) and ion charges (in the range 1–14) are presented. [ABSTRACT FROM AUTHOR]