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Abstract.A detailed study has been performed for estimating the orbital energies, positions and shifts of the Lyman lines of C 5+ , Al 12+ and Ar 17+ under strongly coupled plasma with a view to understand such line positions and shifts obtained in laser produced plasma experiments. The effect of strongly coupled plasma has been treated within the Ion Sphere (IS) model. Both non-relativistic and relativistic methods have been used for estimating the spectral properties. Theoretical estimates with IS model of the plasma are in conformity with the results of laser plasma experiments on these highly stripped ions. The experimental data for the systems have also been compared with the theoretical estimates using Debye screening model of the plasma with spatial confinements which gives additional restrictions to the wave functions at finite boundaries. PACS

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.

Systematic investigations have been performed to study the effect of strongly coupled plasma on the dynamic polarizabilities, low-lying energy levels, oscillator strengths, and transition probabilities for the helium isoelectronic ions . An ion-sphere (IS) model of the plasma has been adopted and time-dependent perturbation theory has been applied to calculate the energy levels and other transition properties. Systematic trend is observed for the spectroscopic properties along the isoelectronic sequence under a given plasma strength and also for a given ion under different plasma strengths. The ionization potential for a given ion is found to decrease, and the number of bound excited states has become finite under increased plasma strengths. The spectral line shifts under such plasma environment have been calculated.

ABSTRACT:The effect of strongly coupled plasma on the energy levels, dynamic polarizabilities, oscillator strengths, and transition probabilities of a number of hydrogenic ions is estimated, using the ion-sphere (IS) model. The transition properties are calculated using time-dependent variation perturbation theory.

The effect of plasma environment on the ground state energies of exotic systems ppµ, ddµ and ttµ has been analyzed within a generalized three-body formalism using multi-term correlated basis sets. The Debye screening model of the plasma has been adopted for such a study. The binding energies of p with pµ, d with dµ and t with tµ have been estimated for a range of values of the Debye screening parameters. The systems tend towards instability for increased screening. The effect of particle correlation has been investigated in detail and is found to play important role for the stability in these systems.

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