Effect of Debye plasma on the doubly excited states of highly stripped ions

Abstract

Pilot calculations have been performed to study the effect of surrounding plasma on several doubly excited states for a few astrophysically important, highly stripped ions of helium isoelectronic sequence Al The effect of the plasma background is taken care of using the Debye screening model which admits of a wide variety of plasma conditions. Transition energies as well as the analytical wave functions of the doubly excited states have been obtained from a study of the pole positions of the collective oscillation modes in the two-electron charge cloud under a time-dependent harmonic perturbation. The response properties of the system are analyzed from the linearized version of a suitably constructed variational functional. Most of the calculated data are new. Our results agree well with the relatively few existing experimental and theoretical data for the free ions. The general trend of the results show systematic behavior with respect to increased plasma strength, and the data may be useful from the astrophysical viewpoint. The doubly excited state wave functions have been used to calculate the Coulomb repulsion integrals to check their consistency and may be useful for evaluating other physical properties connected with transitions and also estimating the rate coefficients for dielectronic recombination processes, which play a major role in the diagnostic determination of high-temperature plasmas.

Bound states of helium atom in dense plasmas

“…A particular value of the screening parameter D corresponds to the range of plasma conditions, as the Debye parameter is a function of electron density and electron temperature. For two-component plasmas near thermodynamic equilibrium, the Debye length D can be written as [4,6,16,17]…”

Unnatural parity states of helium with screened Coulomb potentials

“…As used in our earlier works, in the present calculation, we employ screened Coulomb (Yukawatype) potentials obtained from the Debye shielding approach to consider plasma effect. Detail applications of Debye screening on the investigation in atoms-in-plasmas are available in the earlier investigations ( [1][2][3][4][5][6][7][8][17][18][19][20][21][22][23][24], references therein). In this work, the resonance parameters are extracted using the CI-type basis function in the framework of the stabilization method [25][26][27].…”

Atomic structure under external confinements: Effect of plasma

“…While dipole polarizability increases in a Debye plasma, it decreases for the strongly coupled plasma described by IS model. The behavior of oscillator strength as reflected in Figures 7 and 8 is also opposite for the Debye model compared with that for IS model 33, 38. While oscillator strength decreases in a Debye plasma, it increases in the strong coupling case.…”