Semiclassical Straight-line Trajectory Method Research Articles

The influence of quantum effects on inelastic ion–ion collisional excitations in dense, high-temperature plasmas

The ion–ion collision processes in dense, high-temperature plasmas are investigated. We focus upon the antiscreening channels of the excitation of a one-electron target by a one-electron projectile. In a pseudopotential framework we take into account plasma-screening effects as well as quantum effects of diffraction and symmetry. The semiclassical straight-line trajectory method is applied to the ion projectile path in order to calculate transition probabilities and cross sections. It is a well-known fact that screening reduces the transition probabilities of the ‘bare’ collision process. In contrast to this, the quantum effects incorporated here lead to an enhancement of the transition probabilities. In this paper, we study how these effects compete.

Screening and collective effects on resonant charge-exchange processes in nonideal plasmas

The resonant charge-exchange process by ion–ion collisions is investigated in nonideal plasmas. The interaction Hamiltonian in nonideal plasmas is given by an pseudopotential model that takes into account the plasma screening effect as well as the nonideal collective effect. Screened atomic states of the target and projectile ions in nonideal plasmas are obtained by the variational principle and perturbational analysis. The semiclassical straight-line trajectory method is used to describe the behavior of the projectile ion. It is found that the resonant charge-exchange probability in nonideal plasmas described by the pseudopotential is smaller than that in ideal plasmas described by the Debye–Hückel potential. The maximum position of the resonant charge-exchange probability, i.e., the position which takes place the resonant change-exchange process, is found to recede from the target ion with an increase of the nonideal effect.

Nonthermal effects on occurrence scattering time in generalized Lorentzian distribution plasmas

Nonthermal effects on the occurrence time advance for the elastic electron–ion collisions in generalized Lorentzian (kappa) distribution plasmas are investigated using the first-order eikonal analysis. The electron–ion interaction potential in the Lorentzian plasmas is obtained by the introduction of the plasma dielectric function (εκ). The semiclassical straight-line trajectory method is applied to the path of the projectile electron in order to obtain the eikonal phase and the scattering amplitude as functions of the impact parameter, Debye length, and spectral index (κ), and collision energy. The occurrence time advance is found to be increased with the increasing scattering angle. It is found that the occurrence time advance has the maximum value for the case of the thermal Maxwellian distribution plasmas. It is also found that the occurrence time advance decreases with the decreasing spectral index, i.e., increasing the nonthermal character of the plasma.

Quantum Effects on Collisional Orientations in Dense Plasmas

Quantum effects on the orientation phenomena for the 1s → 2p±1 collisional excitations in electron-hydrogenic ion scatterings are investigated in dense plasmas. An effective pseudopotential model taking into account both the quantum-mechanical effect and the plasma screening effect is applied to describe the electron-ion interaction potential in dense plasmas. The semiclassical straight-line trajectory method is applied to the motion of the projectile electron in order to investigate the variation of the orientation parameter as a function of the scaled impact parameter, thermal de Broglie wavelength, Debye length, and projectile energy. The result shows that the preference for the 1s → 2p-1 transition is significantly reduced with increasing projectile energy. For large impact parameters, the quantum mechanical effect reduces the preference for the 1s → 2p-1 transition. However, the preference for the 1s → 2p-1 transition is also increased with increasing quantum mechanical effect for small impact parameters

Dynamic plasma screening effects on electron–ion collisional ionizations in a generalized Lorentzian distribution plasma

Dynamic plasma screening effects on semiclassical ionization probabilities for electron-impact ionization of hydrogenic ions are investigated in a generalized Lorenzian (kappa) distribution plasma. The projectile–target interaction Hamiltonian is obtained by introduction of the longitudinal plasma dielectric function. A semiclassical straight-line trajectory method is applied to the path of the projectile electron and the bound electron is treated quantum mechanically. The semiclassical ionization probability is obtained as a function of the impact parameter, projectile energy, spectral index, and Debye length. It is found that the non-Maxwellian effect is quite small for low plasma temperatures. However, the non-Maxwellian effect is significant for high plasma temperatures. It is also found that the dynamic plasma screening effect is increased with decreasing the spectral index.

Eikonal elastic scattering cross section for electron–dust grain collisions in dusty plasmas

Plasma screening effects on electron–dust grain elastic collisions in dusty plasmas are investigated using the eikonal method. Attractive interaction between the projectile electron and its own image charge inside the dust grain is included to obtain the total interaction potential between the projectile electron and the dust grain. The semiclassical straight-line trajectory method is applied to the path of the projectile electron in order to investigate the variation of the eikonal phase as a function of the impact parameter, dust charge, and Debye length. The eikonal elastic cross section substantially decreases with a decrease of the Debye length. It is also found that the position of the maximum cross section is shifted to a higher energy region with increasing the dust charge.

Dynamic plasma screening effects on electron-ion Coulomb bremsstrahlung in the Lorentzian distribution plasma

Dynamic plasma screening effects are investigated on classical bremsstrahlung electron-ion Coulomb scattering in a generalization Lorentzian (kappa) velocity distribution plasma. The electron-ion interaction potential is obtained by introduction of the plasma dielectric function. A semiclassical straight-line trajectory method is applied to the path of the projectile electron. The results show that the differential bremsstrahlung radiation cross section including the dynamic plasma screening effect is increased as an increase of the spectral index κ. In other words, the radiation spectrum in a thermal distribution plasma is found to be stronger than that in the nonthermal distribution plasma. It is also found that the plasma screening effects on the bremsstrahlung are more effective for the hard photon radiation. When the projectile velocity is greater than the electron thermal velocity, then, the interaction potential is almost unshielded.

Dynamic plasma screening effects on electron–ion collisional excitations in a generalized Lorenzian (kappa) distribution plasma

Dynamic plasma screening effects are investigated on 1s→2p dipole transition probabilities for electron-impact excitation of hydrogenic ions in a generalized Lorenzian (kappa) velocity distribution plasmas. The electron–ion interaction potential is obtained by introduction of the plasma dielectric function. A semiclassical straight-line trajectory method is applied to the path of the projectile electron in order to visualize the dynamic plasma screening effects on the semiclassical transition probabilities as a function of the impact parameter and the collision energy. The transition probability including the dynamic plasma screening effect is found to be always greater than that including the static plasma screening effects. It is also found that the dynamic plasma screening effects on the electron–ion collisional excitations in the Lorenzian velocity distribution plasmas are more effective than those in the Maxwellian velocity distribution plasmas.

Dynamic screening effects on antiscreening excitations for ion–ion collisions in dense plasma

In dense plasmas, dynamic plasma screening effects are investigated on antiscreening channels for excitation of a one-electron ion target by a one-electron ion projectile. The ion–ion interaction potential is considered by the introduction of the longitudinal plasma dielectric function. A semiclassical straight-line trajectory method is applied to the ion projectile path in order to visualize the dynamic plasma screening effects on the transition probabilities in dense plasmas as a function of the impact parameter and the collision energy. The transition probabilities including the dynamic plasma screening effects are found to always be greater than those including the static plasma screening effects. When the projectile velocity is greater than the electron thermal velocity, the interaction potential is almost unshielded. The difference between the dynamic and static plasma screening effects is more significant for low-energy projectiles. It is also found that the quadrupole transitions (dipole-quadrupole and quadrupole–quadrupole) show the double peaks due to the node of the 2s radial wave function.

Plasma screening effects on eikonal phase for electron-ion elastic collisions in weakly coupled plasmas

Eikonal approximation is applied to investigate elastic electron-ion collisions in weakly coupled plasmas. Plasma screening effects on eikonal phase are investigated for eikonal differential elastic scattering cross sections. The electron-ion interaction potential in weakly coupled plasmas has been obtained by the introduction of the longitudinal plasma dielectric function. The semiclassical straight-line trajectory method is applied to the path of the projectile electron in order to investigate the variation of the eikonal phase as a function of the impact parameter and the plasma parameters. In the first-order eikonal approximation, the dynamic plasma screening effect is identical to the static screening effect obtained by the Debye–Hückel potential. The eikonal differential elastic cross section substantially decreases with an increase in the projectile energy and increases as the plasma screening effect decreases through the Debye length. The plasma screening effects are more significant for large impact parameters.

Antiscreening channels for ion–ion collisional excitations in dense plasmas

Plasma-screening effects are investigated on antiscreening channels for excitation of a one-electron target by a one-electron projectile in dense plasmas. The interaction Hamiltonian in dense plasmas is obtained by an appropriate form of the nonspherical Debye–Hückel potentials. Semiclassical straight-line trajectory method is applied to the ion projectile path in order to visualize the antiscreening transition probability in dense plasmas as a function of the impact parameter and the collision energy. The plasma screening effects reduce the transition probabilities, especially, in the dipole–dipole transition. The maximum position of the transition probability is receding from the target nucleus with increasing projectile energy for the dipole–dipole and dipole–quadrupole excitations. However, in the quadrupole–quadrupole excitation, the maximum position is getting closer to the target nucleus with increasing projectile energy. The quadrupole transitions (dipole–quadrupole and quadrupole–quadrupole) show the second maximum which is due to the double peaks of the 2s radial distribution function.

Dynamic plasma screening effects on semiclassical inelastic electron–ion collisions in dense plasmas

In dense plasmas, dynamic plasma screening effects are investigated on 1s→2p dipole transition probabilities for electron-impact excitation of hydrogenic ions. The electron–ion interaction potential is considered by introduction of the plasma dielectric function. A semiclassical straight-line trajectory method is applied to the path of the projectile electron in order to visualize the semiclassical transition probability as a function of the impact parameter, projectile energy, and plasma parameters. The transition probability including the dynamic plasma screening effect is always greater than that including the static plasma screening effect. When the projectile velocity is smaller than the electron thermal velocity, the dynamic polarization screening effect becomes the static plasma screening effect. When the projectile velocity is greater than the electron thermal velocity, then the interaction potential is almost unshielded. The difference between the dynamic and static plasma screening effects is more significant for low-energy projectiles. It is also found that the static plasma screening formula obtained by the Debye–Hückel model overestimates the plasma screening effects on the atomic excitation processes in dense plasmas.

Plasma-screening effects on semiclassical ionization probabilities for the electron-impact ionization of hydrogenic ions in dense plasmas

Plasma-screening effects are investigated on semiclassical ionization probabilities for electron-impact ionization of hydrogenic ions in dense plasmas. The projectile - target interaction Hamiltonian is obtained by an appropriate form of the non-spherical Debye - Hückel model. Semiclassical straight-line trajectory method is applied to the projectile path in order to visualize the ionization probability in dense plasmas as a function of the impact parameter and Debye length. The final state of the ejected electron is represented by a plane wave solution normalized in the energy scale. The plasma-screening effect on the ionization probability is appreciably increased with increasing projectile energy. The maximum position of the ionization probability recedes from the nucleus as the projectile energy increases.

Minima of the orientation phenomena for directs-pelectron-ion excitations in dense plasmas

Close-encounter effects on electron-ion s\ensuremath{\rightarrow}p oriented excitations in dense plasmas are investigated using a first-order semiclassical straight-line trajectory method. Plasma-screened interaction potential is given by the classical nonspherical Debye-H\uckel model. Without using the dipole approximation, the transition probabilities and orientation parameters are obtained, for various Debye lengths and projectile energies. Including the plasma-screening effects, the transition probabilities are increased for 1s\ensuremath{\rightarrow}2${\mathit{p}}_{+1}$ transitions and decreased for 1s\ensuremath{\rightarrow}2${\mathit{p}}_{\mathrm{\ensuremath{-}}1}$ transitions. The close-encounter effects appreciably change the transition probabilities and orientation parameters for small impact parameters. It is found that the 1s\ensuremath{\rightarrow}2${\mathit{p}}_{+1}$ transition probabilities and orientation parameters have minima that correspond to the complete 1s\ensuremath{\rightarrow}2${\mathit{p}}_{\mathrm{\ensuremath{-}}1}$ transitions.

Electron–ion collisional excitations in strongly coupled plasmas using the ion-sphere model

In strongly coupled plasmas, screening effects are investigated on 1s→2p dipole transition probabilities for electron-impact excitation of hydrogenic ions. Electron–ion interaction is described by the ion-sphere model potential. Behavior of the projectile electron is represented by the semiclassical straight-line trajectory method. Variation of the transition probabilities is determined as a function of the plasma-screening strength through the size of the ion sphere. The transition probabilities are increased with an increase of the ion-sphere radius and the projectile energy. These results, in strongly coupled plasmas, are similar to the screening effects on 1s→2p dipole transition probabilities for electron–ion excitations in weakly coupled plasmas described by the classical Debye–Hückel model.

Semiclassical transition probabilities for the electron-impact excitation of hydrogenic ions in dense plasmas

Plasma-screening effects are investigated on semiclassical transition probabilities for electron-impact excitation of hydrogenic ions in dense plasmas. The electron–ion interaction potential is obtained by a nonspherical Debye–Hückel model of the screened Coulomb interaction for the interesting domain of the Debye length Λ/aZ≥10. Semiclassical straight-line trajectory method is used to describe the behavior of the projectile electron. The screening effect is increased with increasing the projectile energy. The plasma-screening effect on the optically allowed (dipole) transition (1s→2p) is found to be more effective than that on the optically forbidden transition (1s→2s). For 1s→2s transition, the maximum position of the transition probability is almost unchanged with increasing or decreasing the projectile energy and plasma-screening effect. However, for 1s→2p transition, the maximum position of the transition probability has receded from the nucleus as the projectile energy increases.