Oscillator Strengths And Resonance States Of Two-electron Systems In Plasma Environments

The study of atomic processes in plasma environments has gained considerableattention in the recent years. With the recent advancement in laser plasmas and withthe current interest on the study of atomic systems in plasma environments, it isimportant to investigate the effect of plasma environments on the quadrupoleoscillator strengths of helium atom. In the space environment, however, plasmas aregenerally observed to possess a non-Maxwellian high-energy tail that can be wellmodeled by a generalized Lorentzian （or kappa） distribution function containing thespectral index. It is important to investigate the nonthermal effects on atomicstructures in astrophysical plasmas in many areas of physics, such as atomic physics,astrophysics, and plasma physics. In view of the importance of the doubly excitedstates in astrophysical plasmas, it is of great interest to study resonance states oftwo-electron systems under the influence of Lorentzian astrophysical plasmaenvironments.In this article, the influence of Debye potentials on the quadrupole oscillatorstrengths of helium atom is investigated using highly correlated wave functionswithin a framework of a variational method. We present the quadrupole oscillatorstrengths for all possible n¹S–m¹D, n³S–m³D, n¹P–m¹P, n³P–m³P,n¹D–m¹D, and n³D–m³D transitions involving states with nï¿¡5and mï¿¡5ofhelium atom for different screening parameters. The calculations are based uponhighly correlated exponential wave functions in which exponent is supported bywidely used quasi-random process. Convergence of our calculation has beenexamined with the increasing number of terms in wave functions. In free-atomiccase our results are in good accord with the available results. The quadrupoleoscillator strengths for the3^1,3D–n^1,3D（n=4,5） and4^1,3D–5^1,3D transitions areevaluated for the first time using the correlated exponential wave functions. Thequadrupole oscillator strengths of helium in the screening environments are alsoreported for the first time. In the screening environments, the quadrupole oscillatorstrengths show interesting behaviors with increasing screening parameters.In this work, we investigate the plasma screening effects on the doubly excitedresonance states of helium atom and helium-like ions in Lorentzian plasmas usinghighly correlated wave functions. The stabilization method is used to extractresonance parameters. Results are presented as functions of spectral index andplasma screening parameter. In the present study, we investigated the plasmascreening effects on the doubly excited states of the hydrogen negative ion and helium immersed in Lorentzian astrophysical plasma environments using highlycorrelated wave functions in the framework of the stabilization method. The doublyexcited2s²¹S^eand2p²¹S^eresonance states of two-electron atomic system He andtwo-electron ionic systems H^-, Li·+, Be²⁺and B³⁺as functions of the spectral indexand plasma parameter are presented for the first time in the literature. Resonanceparameters show interesting behaviors in Lorentzian plasma environments. We hopeour findings will provide useful information for future studies on this topic.This work is innovative. The quadrupole oscillator strengths for the^1,3S–^1,3D,^1,3P–^1,3P and^1,3D–^1,3D transitions of He for various screening parameters arereported for the first time in the literature. The quadrupole oscillator strengths forthe3^1,3D–n^1,3D（n=4,5） and4^1,3D–5^1,3D transitions are evaluated for the first timeusing the correlated exponential wave functions. In the screening environments, thequadrupole oscillator strengths show interesting behaviors with increasing screeningparameters. The2s²¹S^eand2p²¹S^eresonance states of two-electron atomic systemHe and two-electron ionic systems H^-, Li⁺, Be2⁺and B³⁺as functions of the spectralindex and plasma parameter are presented for the first time in the literature.Resonance parameters show interesting behaviors in Lorentzian plasmaenvironments.This study on oscillator strengths and resonance states of two-electron atomicsystems in plasma environments is of great importance. The findings will provideuseful information to the research of atomic and molecular physics, plasma physicsand astrophysics etc. The results are more accurate than earlier work because of theuse of correlated wave functions to represents correlation effects on the chargedparticles. With the improved experimental technique, and with the wide applicationof screened Coulomb potentials in different areas of physics and chemistry, webelieve our results will provide useful information to the research communities ofplasma physics, atomic physics, chemical physics, few-body physics, andastrophysics.