Debye Plasma Environment Research Articles

Hyperpolarizability of two electron atoms under spherically confined Debye plasma

Pilot calculations on the hyperpolarizability of He, the first neutral member of the two electron sequence, have been performed under spherical confinement with a view to analyse the effect of pressure on such non linear optical properties. Detailed investigations have also been performed for the first time on the hyperpolarizability due to the effect of screened Coulomb potential obtained from a surrounding Debye plasma environment. Variation perturbation theory within coupled Hartree-Fock scheme has been adopted to estimate the non linear optical properties under such external confinement. For a given plasma coupling strength, the hyperpolarizability value is found to reduce systematically with decrease of radius of confinement, while the same is found to increase continuously with increasing plasma coupling strength determined by gradual enhancement of the screening parameter for a given radius of confinement. Under strong confinement the hyperpolarizability value is found to be negative. The estimated free atom hyperpolarizability is consistent with the existing coupled Hartree-Fock result.

Lowest lying 1De resonance of H- in Debye plasma

Electron-hydrogen scattering has been investigated in Debye plasma environment employing the close-coupling approximation. Two models, viz., 6-state CCA and 9-state CCA have been used. Plasma screening has been taken into account via Debye-Huckel model potential. The lowest lying \(^1{\rm D}^{{\rm e}}\) auto-detaching resonance of the hydrogen negative ion has been successfully predicted for various plasma conditions. The resonant state changes to shape resonance for Debye scattering lengths less than a critical value.

Combined effect of Debye plasma environment and external electric field on hydrogen atom

We consider weakly coupled plasmas, characterized by Debye–Huckel model potential, and an external electric field along z-axis. Due to plasma environment the energy levels of atom are shifted up, bound states are merged to continuum. For external electric field the excited energy levels also split up; degenerate energy eigenvalues become nondegenerate. In the presence of external electric field, energy levels are shifted up and down, except ground state. The ground state energy value is shifted only down. Therefore, it is very interesting to study the combined effect of plasmas and external electric field on a simple atom (hydrogen). To calculate the energy levels and the corresponding states, we expand the wave function in terms of linear combination of the basis functions. The basis is generated by hydrogenic wave functions. Here, we estimate various plasma surroundings and electric field strengths. We observe converged results for the basis size 45, with angular momentum states up to eight.

P-wave auto-detaching resonances of H− below the n = 2 threshold in a Debye plasma medium

p-wave electron–hydrogen scattering has been investigated in a Debye plasma environment employing a close-coupling approximation. Three different basis sets have been used to estimate the resonance parameters. Plasma screening has been taken into account via the Debye–Hückel model potential. Auto-detaching 1, 3Po resonances of the hydrogen negative ion below the n = 2 threshold have been studied under various plasma conditions. The present predicted resonance energies and widths are in close agreement with those of Kar and Ho (2006 Few Body Syst. 40 13).

Formula omitted] and [formula omitted] states of two electron atoms under Debye plasma screening

Extensive non-relativistic variational calculations for estimating the energy values of 2 pnd ( D o 1 , 3 ) states [ n = 3 – 6 ] of two electron atoms (He, Li + , Be 2 + ) and 2 pnp ( P e 1 ) [ n = 3 – 8 ] and 2 pnp ( P e 3 ) states [ n = 2 – 7 ] of Be 2 + under weakly coupled plasma screening have been performed using explicitly correlated Hylleraas type basis. The modified energy eigenvalues of P e 1 , 3 states arising from two p electrons of Be 2 + ion and D o 1 , 3 states due to 2 pnd configuration of Li + and Be 2 + ion in the Debye plasma environment are being reported for the first time. The effect of plasma has been incorporated through the Debye screening model. The system tends towards gradual instability and the number of bound states reduces with increasing plasma coupling strength. The wavelengths for 2 pn ′ p ( P e 1 ) [ n ′ = 3 – 8 ] → 2 pnd ( D o 1 ) [ n = 3 – 6 ] and 2 pn ′ p ( P e 3 ) [ n ′ = 2 – 8 ] → 2 pnd ( D o 3 ) [ n = 3 – 6 ] transitions in plasma embedded two electron atoms have also been reported.

2pnp (1,3Pe) states of neutral He and Li+ ions under Debye plasma screening

The energy eigenvalues of doubly excited 2pnp (1Pe) (n = 3–8) and 2pnp (3Pe) (n = 2–7) bound states of a neutral helium atom and singly ionized lithium atom are estimated under weakly coupled plasma screening for the first time using an explicitly correlated Hylleraas-type basis in the framework of the Rayleigh–Ritz variational principle. The Debye screening model has been employed to include the effect of plasma background. Improvement over the existing approximated theoretical results has been achieved for the above-mentioned states of neutral helium under Debye plasma screening. The modified energy eigenvalues of 1,3Pe states arising from two p electrons of a Li+ ion in the Debye plasma environment are being reported for the first time.

Application of variational method for three-color three-photon transitions in hydrogen atom implanted in Debye plasmas

Multiphoton processes, where transparency appears, have long fascinated physicists. Plasma screening effects are investigated on three-color three-photon bound-bound transitions in hydrogen atom embedded in Debye plasmas; where photons are linearly and circularly polarized, two left circular and one right circular. All possible combinations of frequency and polarization are considered. Analytical wave functions are used for initial and final states along with the pseudostate wave functions for intermediate states. The analytical wave functions are obtained from the modified wave functions for screening Coulomb potential (Debye model) using Ritz variational method. Here, we have found three-photon transparency for lower values of Debye length. This type of phenomenon occurs due to energy level shifting in the presence of Debye plasma environments. The description of resonance enhancements and three-photon transparency is reported in the present context along with the region of resonance enhancements and three-photon transparency.

On the Appearance of a Cooper Minimum in the Photoionization Cross Sections of the Plasma-Embedded Li Atom

The plasma screening effect is found to uncover a Cooper minimum in the photoionization cross sections from the ground state of the Li atom embedded in Debye plasma environment. The variation of the location of this minimum with Debye screening length is discussed and analyzed in terms of the instability of the ground state.

Photoionization of the excited He atom in Debye plasmas

We present theoretical photoionization cross sections for He 1s2s 1S and He 1s2p 1P states in a Debye plasma environment by the complex coordinate rotation method, using a finite L 2 basis set constructed from one electron Laguerre orbitals. The plasma environment is found to appreciably influence the photoionization cross sections near the ionization threshold. In this regard, the photoionization cross sections of isolated He are compared with other theoretical and experimental results. Our results are in good agreement with the previous results. A new minimum appears in the photoionization cross section curve for the metastable 1s2s 1S state. Results are given for the S- and D-wave partial photoionization for the excited 1s2p 1P state.

Hydrogen atoms in Debye plasma environments

Plasma-screening effects are investigated on hydrogen atoms embedded in weakly coupled plasmas. In the present context, bound state wave functions are introduced related to the screening Coulomb potential (Debye model) using the Ritz variation method. The bound energies are derived from an energy equation, which contains one unknown variational parameter. To calculate the parameter numerically, fixed-point iteration scheme is used. The calculated energy eigenvalues for various Debye lengths agree well with the other available theoretical results. The radial wave functions and radial probability distribution functions are presented for different Debye lengths. The outcomes show that the plasma affects the embedded hydrogen atom.

Two-photon transitions in hydrogen atoms embedded in weakly coupled plasmas

The pseudostate method has been applied to calculate energy eigenvalues and corresponding eigenfunctions of the hydrogen atom in Debye plasma environments. Resonant two-photon transition rates from the ground state of atomic hydrogen to 2s and 3s excited states have been computed as a function of photon frequency in the length and velocity gauges for different Debye lengths. A two-photon transparency is found in correspondence to each resonance for 1s–3s. The transparency frequency and resonance enhancement frequency vary significantly with the Debye length.

Electron–positronium scattering in Debye plasma environment

Electron–positronium scattering has been investigated in the Debye plasma environment employing the close-coupling approximation. Three models, viz. 3-state CCA, 6-state CCA and 9-state CCA, have been employed. The 2s21Se autodetaching resonant state of the positronium negative ion has been successfully predicted for various plasma environments. The position of the resonance for different Debye lengths are in close agreement with those of Kar and Ho [S. Kar, Y.K. Ho, Phys. Rev. A 71 (2005) 052503].

Bound States and Resonance States of H^- and He Embedded in Debye Plasma Environments

The doubly excited S-, P- resonance states of H i and the doubly-excited S-, P-, D-resonance states of He embedded in Debye plasma environments have been investigated for by calculating the density of resonance states using stabilization method. The ground states of H i and the bound excited states of He atom in plasmas for various Debye lengths have also been estimated in the framework of Rayleigh-Ritz variational method and by using a quasi-random process. Highly correlated wave functions have been used to represent the correlation efiects between the charged particles. Some of our calculated results on the bound states and resonance states are highlighted in this paper and the detail results will be presented at the conference. DOI: 10.2529/PIERS060907063228

Photoionization of Li and Na in Debye plasma environments

A calculation of the photoionization cross sections is presented for alkali-metal atoms such as Li and Na in plasma environments. The computational scheme is based on the complex coordinate rotation method. A model potential formalism has been used to simplify the computational complexity of the problems of making quantitative predictions of properties and interactions of many electron systems in Debye plasmas. The plasma environment is found to appreciably influence the photoionization cross sections. In this regard the photoionization cross sections of isolated atoms are also discussed that is found to be in good agreement with the previous theoretical results. It is observed that the strong plasma screening effect remarkably alters the photoionization cross sections near the ionization threshold. The Cooper minimum in the photoionization cross sections of Na shifts toward the higher energy as the plasma screening effect increases. For Li, the Cooper minimum is uncovered in strong plasma environments. This is the first time such structures have been determined.

S-wave resonances in the positron–hydrogen system with screened Coulomb potentials

We have made a first calculation for S-wave resonances in positron–hydrogen scattering under the influence of Debye plasma environments. A screened Coulomb potential obtained from the Debye model is used to represent the interaction between the nucleus, the electron and the positron. Hylleraas-type wavefunctions are used to represent the correlation effect between the charge particles. The stabilization method is used to calculate the density of resonance states, from which resonance energies and widths are deduced. We have found two resonances of which one is associated with the hydrogen n = 2 threshold, and the other one is found lying below the Ps(2S) threshold. The resonance parameters (energies and widths) calculated for various Debye lengths are reported.

AutoionizingSe1resonance ofH−in Debye plasma environments

We have made an attempt to investigate atomic resonances in various Debye plasma environments. The 2 s(2) (1)S(e) autoionization resonance for a two-electron system H- is determined by calculating the density of resonance states using the stabilization method. Highly correlated Hylleraas-type wave functions are used to represent the correlation effects between the three charged particles. The calculated resonance energies and widths for the various Debye parameters ranging from infinity to a small value are reported.

Negative hydrogen and helium in a variety of debye plasmas

Aspects of the influence of a strong Debye plasma environment on the negative hydrogen ion and the neutral helium atom have been studied. Contrary to earlier work, in the present calculation all interactions have been screened. This increases the stability of the systems to the extent that neither the H- ion nor the ground state of helium will lose an electron by pressure ionization. It has been found that the charge distribution of H- remains remarkably constant over a vast range of values of the Debye parameter D. © 1996 John Wiley & Sons, Inc.