Dynamic polarizability and electric multipolar transitions in two electron atoms under exponential cosine screened coulomb potential

Detailed investigations on the frequency dependent polarizabilities, transition energies, oscillator strengths, and transition probabilities of two electron systems He, Be2+, C4+, and O6+ under electric dipolar (E1) and quadrupolar (E2) excitations have been performed using exponential cosine screened coulomb potential with a view to understand the structural behaviour of such systems due to external confinement produced by plasma environment. Time dependent coupled Hartree–Fock theory within a variational framework has been adopted for studying the first three low lying excited states 1s2:1Se→1snp:1Po (n = 2, 3, 4) and 1snd:1De (n = 3, 4, 5) under such excitations. Quantitatively, the effect of confinement produced by the external plasma has been taken care of by considering the change in atomic potential through plasma screening, directly related to the coupling strength of the plasma with the atomic charge cloud. With increased plasma screening, a gradual destabilisation of the energy levels with subse...