Bound and resonance states of highly charged H- and He-like ions under weakly coupled plasma environment

The position of bound $1\mathrm{sns}$ ($n=1-5$) states as well as doubly excited resonance $2\mathrm{sns}$, $2\mathrm{pnp}$ ($n=2-3$) states of ${\hspace{0.17em}}^1{S}^e$ symmetry has been determined for highly charged He-like ions ($C^{4+}$, ${\mathrm{Mg}}^{10+}$, ${\mathrm{Al}}^{11+}$, ${\mathrm{Si}}^{12+}$, $S^{14+}$, and Ar¹⁶⁺) along with their respective one-electron thresholds ($1s$, $2s$, and $2p$) under weakly coupled plasma environment. These particular ions and their respective charge states are selected due to their frequent occurrence in astrophysical and laboratory plasmas. Ritz variational method with multi-exponent explicitly correlated Hylleraas type basis and pure-exponential basis set are adopted for tackling He- and H-like ions, respectively. The resonance width of a few low-lying resonance states is determined using the stabilization method under different plasma conditions. Ionization potential depression is noted for both the bound and resonance states of the plasma-embedded ions. It is evident that the width (or the lifetime) of the considered resonance states originating from different dominant configurations follows different patterns w.r.t. the plasma screening length.