Collective Screening Effects Research Articles

Influence of semiclassical plasma on the energy levels and radiative transitions in highly charged ions

Considering the quantum effects of diffraction and the collective screening effects, the potential of test charge in semiclassical plasmas is derived. It is generalized exponential screened Coulomb potential. Using the Ritz variational method incorporating this potential, the effects of semiclassical plasma on the energy levels and radiative transitions are investigated systematically, taking highly charged H-like ion as an example. The Debye plasma model is also employed for comparison purposes. Comparisons and analysis are made between these two sets of results and the differences are discussed.

Electron capture processes in strongly coupled semiclassical plasmas

The electron captures by projectile ions from hydrogenic ions are investigated in strongly coupled semiclassical plasmas. The electron capture radius by the projectile ion is obtained by the effective screened pseudopotential model taking into account both the plasma screening and quantum effects. The semiclassical version of the Bohr-Lindhard method is applied to obtain the electron capture probability. The impact-parameter trajectory analysis is applied to the motion of the projectile ion in order to visualize the electron capture radius and capture probability as functions of the impact parameter, thermal de Broglie wavelength and Debye length. The results show that the quantum and plasma screening effects significantly reduce the electron capture probability and the capture radius. It is found that the electron capture position is shifted to the core of the projectile ion with increasing the thermal de Broglie wavelength. It is also found that the quantum effects on the electron capture probability are more significant than the collective screening effects on the electron capture probability. The electron capture probability is found to be significantly increased with an increase of the charge.

Plasma screening effect in ion-ion scattering

When a plasma is extremely dense or hot, the electrons lose their efficiency for stopping heavy charged particles. The main process for their slowing down then is the small-angle ion-ion scattering, where the bare Coulomb cross section becomes infinite as ${\ensuremath{\theta}}^{\ensuremath{-}4}$. The purpose of this paper is to evaluate the collective screening effects which make the ion Coulomb cross section finite. The calculations are performed in the random-phase approximation and show that the Coulomb cross section is essentially cut off for energy transfers smaller than $\ensuremath{\hbar}{\ensuremath{\omega}}_{p}$, where ${\ensuremath{\omega}}_{p}$ is the plasma frequency of the ions.