Spectral lines behavior of Be I and Na I isoelectronic sequence in Debye plasma environment

Abstract

We report the plasma screening effect on the first ionization potential (IP) and [He]2s/sup2/ (/sup1/S/sup0/)→[He]2s2p/2s3p allowed (/sup1/P/sub1/) and inter-combination transitions (/sup3/P/sub1/) in some selected Be-like ions. In addition, we investigate the spectral properties of [Ne]3s (/sup2/S/sub1/2/)→[Ne]np (/sup2P/sub1/2/ and /sup2/P/sub3/2/ for n = 3, 4) transitions in Ca X and Fe XVI ions (Na I isoelectronic sequence) and [He]3s(/sup2/S/sub1/2/)→[He]np (/sup2/P/sub1/2 and /sup2/P/sub3/2/ for n = 2, 3) transitions in Li, B II, and N IV (Li I isoelectronic sequence) under plasma environment. The state-of-the-art relativistic coupled cluster calculations using the Debye model of plasma for electron-nucleus interaction show that (a) the ionization potential decreases sharply with increasing plasma strength and (b) the gap between the [He]2s2 (/sup1/S/sub0/)→[He]2s2p(/sup1,3/P/sup1/) energy levels increases with increasing plasma potential and nuclear charge. It is found that the [He]2s/sup2/ (/sup1/S/sub0/)→2s3p (/sup1,3/P/sub1/) transition energy decreases uniformly with increasing plasma potential and nuclear charge. In other words, the spectral lines associated with 2s-2p (i.e., Δn = 0, where n corresponds to principle quantum number) transitions in Be I isoelectronic sequence exhibit a blue-shift (except for Be I, B II, and the lowest inter-combination line in C III, which exhibit a red-shift), whereas those associated with 2s-3p (i.e., Δn ≠ 0) transitions are red-shifted. Similar trend is observed in Li I and Na I isoelectronic sequences, where spectral lines associated with Δn = 0 (Δn ≠ 0) are blue-shifted (red-shifted). The effect of Coulomb screening on the spectral lines of ions subjected to plasma is also addressed.