Debye Plasma Environment Research Articles

Two-photon transitions in H@C60 in Debye plasma environment

Two-photon transition amplitudes for endohedrally confined plasma-embedded hydrogen are calculated for various values of the incident photon frequencies. Calculations are performed for the plasma-embedded H@C60. Resonance enhancements characteristic of two-photon transitions are observed, and the frequencies for the resonant enhancement of the transitions are noted. The two-photon process for such systems has not been explored earlier. For H@C60 the variation of the transition amplitudes on the frequency of photons and the Debye screening parameter, µ, are shown graphically.

Influence of relativistic effects on photoionization process of hydrogen-like ions in plasma environment

In this study, the photoionization cross sections of C<sup>5+</sup>, Al<sup>12+</sup>, and W<sup>73+</sup> ions in a Debye plasma environment are calculated in the dipole approximation. The main emphasis is placed on investigating the influence of relativistic effects on shape resonances, Cooper minima, and virtual state effects. The relativistic effects lead to fine-structure splittings, allowing the appearance of double-shape resonance peaks in the total cross-section. Because the width and energy position of resonance peak are affected by the near critical screening length, the increase of nuclear charge Z leads to the significant differences in the size, width, and position of the double-shape resonance peak. The energy position of Cooper minimum in the photoelectrons is related to the critical screening length corresponding to the final continuum state. Unlike the deeper minima observed in the total photoionization cross-sections for C<sup>5+</sup> and Al<sup>12+</sup> ions, for the higher nuclear charge of W<sup>73+</sup> ions, the significant fine-structure splitting arising from relativistic effects results in substantial differences in the positions of the Cooper minima in the partial cross-sections. Therefore, when superimposed on the total cross section, these minima appear shallower. The W<sup>73+</sup> ion has a higher nuclear charge, and the screening length related to the virtual state effect is completely different from that of C<sup>5+</sup> ion and Al<sup>12+</sup> ion. Moreover, for the same screening length, there is a significant difference in the virtual state enhancement amplitude between C<sup>5+</sup> ion and Al<sup>12+</sup> ion in the low energy region .

Shannon entropy for hydrogen atom in Debye and quantum plasma environment

The plasma screening effect on Shannon entropy values is studied for atomic states of hydrogen under the more general exponential cosine screened Coulomb (MGECSC) potential, which can be used to model Debye and quantum plasmas. The wavefunctions used in the calculation of Shannon entropy are obtained by solving the Schrödinger equation employing the efficient Numerov technique. Shannon entropy is calculated for hydrogen atom quantum levels using various sets of screening parameters to account for the four different potential forms present in the MGECSC potential. The electron density distributions are considerably altered due to the plasma shielding influence on the embedded hydrogen atoms, and this effect is measured by the shift in Shannon entropy. A greater screening influence on entropy is observed in quantum plasma modeled by the MGECSC potential than that in Debye plasma due to the significant combined effects of screening parameters. Excellent convergence is obtained on comparing our results for plasma-free hydrogen atom with the currently available literature. This study is the first to examine the effects of shielding on Shannon entropy of hydrogen atoms in plasmas modeled by the MGECSC potential. These findings will be important for theoretical and experimental research in the disciplines of atomic physics and plasma diagnostics.

Manipulating the orbital charge-currents of compressed Li and Na atom embedded in quantum plasma

In this study, for the first time, a theoretical investigation is carried out on the persistent orbital charge-currents (cc) and induced magnetic field (imf) of Li and Na atom compressed by spherical confinement, embedded in a quantum plasma. The more general exponential cosine screened Coulomb (MGECSC) potential is considered for interactions in the quantum plasma. There are four different forms of the MGECSC potential in describing Debye and quantum plasmas, but the most general form is used for the most detailed examination. The model potential approach is employed to popularize the interactions of many body electron systems and to overcome the computational difficulty arising from complex electron–electron interactions through a very valid approach. Therefore, the MGECSC potential for the quantum plasma-immersed Li and Na atom is modified within the framework of the model potential approach. The wave equation including the modified potential is solved using the tridiagonal matrix method. The interaction potential between the valence electron and the atomic core alters significantly by the plasma screening effect. This change also creates observable changes in the persistent charge-current (cc) and induced magnetic fields (imf) of Li and Na atom. The effects of plasma screening parameters and spherical confinement strength on the persistent cc and imf are studied in detail. In addition to the effects of plasma and spherical confinement parameters on the spectrum, the cc and imf of Li and Na atom, their critical values, if any, their dominance and alternatives to each other are also discussed in a cause-effect relationship. In the case of stronger spherical confinement, the quantum plasma has a predominant response on the cc and imf compared to a Debye plasma and free-plasma environments.

Optical response of plasma processed quantum dot under the external fields

AbstractWe investigate theoretically the total refractive index changes (TRICs) and the total absorption coefficients (TACs) of two‐electron Gaussian quantum dot (TEGQD) including Gaussian potential confinement generated by GaAs/GaAlAs heterostructure, embedded in Debye and quantum plasma environments modeled by the more general exponential cosine screened Coulomb (MGECSC) potential, under the influence of the external electric and magnetic field. The wave equation is solved within the effective mass approach framework by using Runge–Kutta–Fehlberg method in order to obtain the subband spectra and the electronic wave functions of TEGQD. Nonlinear optical response of TEGQD is obtained through the compact‐density‐matrix formalism within the iterative method. The effects of both Debye and quantum plasma environments in the strong and weak regimes of the external fields are considered and compared throughout the study. The potents of the external electric field, the external magnetic field, the quantum dot width, the barrier height, and the plasma screening on TRICs and TACs resonant frequencies and amplitudes are analyzed. In addition to these analyses, the alternatives to each parameter effects of the model are also elucidated. TRICs and TACs analyze are carried out in a plasma‐free environment, and thus the function of environments with plasma compared to that without plasma is better explained. Thanks to all these reviews, it is elucidated how to and at what ranges perform in terms of the incident photon energy of TEGQD's optimum for TRICs and TACs characters by using plasma, and in which cases it will be an alternative to the external field and geometrical encompassing.

Analytical method for calculating atomic structures based on the variational method for many-electron atomic structure in plasmas

Within the framework of the Hartree–Fock method and the irreducible tensor theory, we have proposed an analytic formula for calculating the nonrelativistic energies of many-electron atoms. The relativistic mass, the one- and two-body Darwin, the spin–spin contact interaction, and the orbit–orbit interaction corrections to the energies are considered to make the results more precise. The angular interactions and spin sums involved in the formula are worked out explicitly using the irreducible theory. A program based on the variational method is developed to calculate the wave functions and atomic structure properties. The energies of the 1sns 1,3S (n = 1–4) and 1snp 1,3P (n = 2–4) states of the exemplary ions Ar16+, Fe24+, and Kr34+ in both Debye plasma and quantum plasma environments are given. Moreover, we analyzed the evolution of plasma screening parameters and provided some rules for practical and rapid evaluation in plasma applications.

Velocity dependent potential effects on two-electron quantum dot in plasmas

In this study, for the first time, the effects of the velocity-dependent potential (VDP) on the energies of a two-electron parabolic quantum dot (TEPQD) in Debye and quantum plasma environments depicted by a more general exponential cosine screened Coulomb (MGECSC) potential are taken into consideration. The Schrödinger equation is modified by combining the MGECSC potential and VDP, solving numerically via the asymptotic iteration method. The Schrödinger equation with VDP is basically another type of one with position-dependent mass. The effects of VDP on two interacting electrons inside the parabolic quantum dot in plasmas are probed by considering the isotropic form factor with the harmonic (ρ(r)=ρ0r2) and constant (ρ(r)=ρ0) form. The alternativeness of the plasma shielding parameters to each other, the confinement parameter of the quantum dot, and the VDP parameters on energies and possible radiations of TEPQD are also discussed.

The optimal ranges for the optical properties of two-electron quantum dot immersed in plasmas

In this study, for the first time, the total refractive index changes (TRICs) and the total absorption coefficients (TACs) of the spherically confined two-electron parabolic quantum dot (TEPQD) embedded in the Debye and quantum plasmas generated by GaAs/GaAlAs heterostructure and modeled through the more general exponential cosine screened Coulomb (MGECSC) potential are analyzed by solving the corresponding wave equation using the tridiagonal matrix method. Two different types of MGECSC potential are used in the calculations. One of them is the most basic form of it obtained by adjusting the potential parameters for modeling the Debye plasma case, and other is the most common form of it in order to model the quantum plasma case. In addition to plasma environment is an important experimental argument in the synthesis and modification of quantum dots (QDs), the results of the screening effects on these and the fact that screening effect can be adjusted are the main motivation of considering the plasma environments in this study. In this context, the effects of external and structural parameters as well as plasma shielding parameters on TRICs and TACs of TEPQD are investigated in detail. The behavior of the external, structure and plasma shielding parameters on TEPQD's optical properties are compared and their alternativeness to each other are studied. The role of the Debye and quantum plasma environments on the behavior of external and structural parameters in consideration of the nonlinear optical properties is also researched. For the nonlinear optical properties of TEPQD, optimal ranges of all parameters, especially plasma shielding parameters, are determined. It is clear that these detailed determinations will also be very important in further theoretical investigations as well as the necessity for experimental applications.

Two-Electron Pseudodot System With Laser Effect in Plasmas

We have studied the two-electron pseudodot (TEPD) system immersed in plasma environments under the influence of a monochromatic linearly polarized laser field. The four different sets, constituted by the potential parameters, of the more general exponential cosine screened Coulomb potential are used to characterize the Debye and quantum plasma environments. The time dependent in the Schrodinger equation arising from the laser field is interchanged to the potential energy term from the kinetic energy term through the dipole approximation and the Kramers–Henneberger transformation. Then, the laser-dressed potential that denotes the effects of the laser radiation field is constituted by using the Ehlotzky approximation. In that case, as the analytical solution is impossible just now due to the complicated form of the Schrodinger equation, the numerical solution is carried out via the asymptotic iteration method. In this paper, the pseudodot system is considered because the quantum dots are very similar to atomic systems, and the pseudoharmonic potential is successful in explaining the atomistic structures. However, it is an important motivation for us that, as well as the importance of the laser–plasma interactions, the laser field is a considerable exciter for radiating, which exhibits remarkable confinement effects. Since, as well as the screening effects exhibited by plasmas on atomic systems, and their significant results, the plasma is a significant experimental argument in manufacturing and modification of the quantum dots, the plasma effects are taken into consideration in this paper. Within these motivations, all parameters that operate on the energies of TEPD system with the laser effect in plasmas are analyzed in detail, and the corresponding results are discussed thoroughly.

Plasma-screening effects on positronium formation**Project supported by the National Natural Science Foundation of China (Grant Nos. 11404223, 11447158, and 11604223) and the Doctoral Program Foundation of Shenyang Aerospace University, China (Grant No. 13YB26).

Plasma-screening effects on positronium (Ps) formation for positron–hydrogen collisions in a Debye plasma environment is further investigated using the screening approximation model with the inclusion of the modified structure of Ps. More accurate Ps formation cross sections (n = 1, 2) are obtained for various Debye lengths from the Ps formation thresholds to 50 eV. The influence of considering modified bound-state wave functions and eigenenergies for the Ps is found to result in the reduction of the Ps formation cross sections at low energies, whereas it cannot counteract the enhancement of the Ps formation by the Debye screening.

Positronium formation in positron-lithium collisions with Debye potentials

SynopsisPositronium (Ps) formation processes in positron-lithium collisions in Debye plasma environments are investigated using the screening approximation model. We present the Ps(1s) formation cross sections in the incident energy range 2-40eV for screening parameters μ=0.00-0.25.

Atomic structure under external confinement: effect of plasma on the spin orbit splitting, relativistic mass correction and Darwin term for hydrogen-like ions

The effect of Debye and quantum plasma environment on the structural properties such as spin orbit splitting, relativistic mass correction and Darwin term for a few iso-electronic members of hydrogen viz. C5 +, O7 +, Ne9 +, Mg11 +, Si13 +, S15 +, Ar17 +, Ca19 + and Ti21 + has been analysed systematically for the first time for a range of coupling strengths of the plasma. The Debye plasma environment has been treated under a standard screened Coulomb potential (SCP) while the quantum plasma has been treated under an exponential cosine screened Coulomb potential (ECSCP). Estimation of the spin orbit splitting under SCP and ECSCP plasma is restricted to the lowest two dipole allowed states while for the other two properties, the ground state as well as the first two excited states have been chosen. Calculations have been extended to nuclear charges for which appreciable relativistic corrections are noted. In all cases calculations have been extended up to such screening parameters for which the respective excitation energies tend towards their stability limit determined by the ionisation potential at that screening parameter. Interesting behavior of the respective properties with respect to the plasma coupling strength has been noted.

An Investigation on the He−(1s2s2 2S) Resonance in Debye Plasmas

The effect of Debye plasma on the 1 s 2 s 2 2 S resonance states in the scattering of electron from helium atom has been investigated within the framework of the stabilization method. The interactions among the charged particles in Debye plasma have been modelled by Debye–Huckel potential. The 1 s 2 s excited state of the helium atom has been treated as consisting of a H e + ionic core plus an electron moving around. The interaction between the core and the electron has then been modelled by a model potential. It has been found that the background plasma environment significantly affects the resonance states. To the best of our knowledge, such an investigation of 1 s 2 s 2 2 S resonance states of the electron–helium system embedded in Debye plasma environment is the first reported in the literature.

Positronium formation in collisions between positrons and alkali-metal atoms (Li, Na, K, Rb and Cs) in Debye plasma environments

Positronium (Ps) formation processes in collisions between positrons and alkali atoms (Li, Na, K, Rb and Cs) in Debye plasma environments have been investigated using the classical trajectory Monte Carlo (CTMC) method for the energy range 1–500 keV. Interactions between the active electron in an alkali atom with the positron have been described using a model potential along with the Debye–Hückel potential. In such a process, positronium formation cross sections have been calculated in unscreened, as well as in Debye plasma, conditions. The results show that the cross sections for positronium formation are significantly affected by Debye screening lengths. Also, positronium formation depends on collision energy and plasma conditions. The effect of Debye plasma environments on such a formation process is explained in terms of the classical trajectory framework.

Hyperpolarizability of two electron atoms under exponential cosine screened coulomb potential

Hyperpolarizability of two electron atoms He, Li+, Be2+, B3+, and C4+ embedded under quantum plasma environment has been calculated for the first time using exponential cosine screened coulomb potential (ECSCP) arising out of the interaction of atomic charge cloud with such an environment. Coupled Hartree-Fock theory within variational scheme has been utilised to estimate such nonlinear optical property for systematic variation of the screening parameter arising out of the coupling strength of the plasma with atomic charge cloud. Hyperpolarizability of the ions increases systematically with increase of the screening parameter. Results have been compared with respect to those obtained from the interaction of atomic systems with a Debye plasma environment giving rise to SCP. Interesting feature is observed for the polarizability and hyperpolarizability values under increasing screening parameters of ECSCP and SCP. Hyperpolarizability values for zero screening compare well with those available for the free ions.

An investigation of antiprotons collisions with positronium atom in Debye plasma environments

The effects of Debye plasmas on antihydrogen formation and ionization processes are investigated in antiprotons ( p¯) and positronium (Ps) collisions. The classical trajectory Monte Carlo method with Debye Huckel potentials has been used for cross section calculations. In this process, antihydrogen formation and ionization cross sections have been calculated in unscreened as well as in Debye plasmas conditions in energies ranging from 1 to 500 keV. Partial cross sections for antihydrogen formation are also calculated which show the largest cross sections correspond to production of antihydrogen in the n = 2 (2s, 2p) states. Comparative study has been carried out to determine the differences of cross sections in screening and unscreening cases. The results show that the cross sections for both antihydrogen formation and positronium ionization depend on Debye screening lengths as well as on collision energies. The effects of plasmas conditions on antihydrogen formation and positronium ionization are explain...

Photoexcitation and ionization of a hydrogen atom confined by a combined effect of a spherical box and Debye plasma

The spectrum of the hydrogen atom confined by a relatively large radius spherical box and Debye plasma environment is obtained by solving the Schrödinger equation by using Bernstein-polynomials (B-polynomials). Response of such confined atoms to laser field is studied using non-perturbative Floquet method. Photoexcitation and ionization are found to depend on the confining parameters, such as radius of the confining spherical box and the screening parameter of Debye plasma.

Shape resonances in the electron-hydrogen system with screened Coulomb potentials

We investigate the shape resonances of the electron-hydrogen system embedded in Debye plasma environments modeled by screened Coulomb potentials. The complex-coordinate rotation method is employed to calculate the resonance parameters and the Hylleraas-type wave functions are used to represent the correlation effects of the two electrons. The ${}^{1}{S}^{e}$ resonance states of H${}^{\ensuremath{-}}$ above the $N=2$--5 thresholds of H atom are investigated and the resonance parameters for a Debye length ranging from infinity to small values are reported. It is shown that the widths of the shape resonances lying above the H($N=4$,5) thresholds exhibit some interesting behaviors in relatively strong screening situations. The possible reason for such phenomena is discussed.

Spectral lines behavior of Be I and Na I isoelectronic sequence in Debye plasma environment

We report the plasma screening effect on the first ionization potential (IP) and [He]2s2 (1S0)→[He]2s2p/2s3p allowed (P11) and inter-combination transitions (P31) in some selected Be-like ions. In addition, we investigate the spectral properties of [Ne]3s (2S1/2)→[Ne]np (2P1/2 and P23/2 for n = 3, 4) transitions in Ca X and Fe XVI ions (Na I isoelectronic sequence) and [He]3s(2S1/2)→[He]np (2P1/2 and P23/2 for n = 2, 3) transitions in Li, B II, and N IV (Li I isoelectronic sequence) under plasma environment. The state-of-the-art relativistic coupled cluster calculations using the Debye model of plasma for electron-nucleus interaction show that (a) the ionization potential decreases sharply with increasing plasma strength and (b) the gap between the [He]2s2 (1S0)→[He]2s2p(1,3P1) energy levels increases with increasing plasma potential and nuclear charge. It is found that the [He]2s2 (1S0)→2s3p (1,3P1) transition energy decreases uniformly with increasing plasma potential and nuclear charge. In other words, the spectral lines associated with 2s-2p (i.e., Δn=0, where n corresponds to principle quantum number) transitions in Be I isoelectronic sequence exhibit a blue-shift (except for Be I, B II, and the lowest inter-combination line in C III, which exhibit a red-shift), whereas those associated with 2s-3p (i.e., Δn≠0) transitions are red-shifted. Similar trend is observed in Li I and Na I isoelectronic sequences, where spectral lines associated with Δn=0 (Δn≠0) are blue-shifted (red-shifted). The effect of Coulomb screening on the spectral lines of ions subjected to plasma is also addressed.

Positronium formation in positron-hydrogen collisions with Debye potentials

Positronium (Ps) formation cross sections (n = 1, 2) in positron-hydrogen collisions in Debye plasma environment are calculated using the screening approximation model for various Debye screening lengths from the Ps formation thresholds to 50 eV. The effect of the screened Coulomb potential on Ps formation process is investigated by using the Debye-Hückel potential. The present results are compared with available theoretical calculations.