Effect of pressure confinement on electronic structure and radiative transitions of Helium-like systems

Abstract In this work, we have addressed the modification of energy levels of neutral helium and He-like carbon (C4+) in ground state, singly excited 1s2p (1,3Po) states and doubly excited metastable bound 2p2 (3Pe) state under an impenetrable spherical cavity that can mimic the effect of pressure confinement. Ritz variational calculations are carried out to estimate the two-electron energy eigenvalues
using Hylleraas-type trial basis set through which the electron correlation is incorporated explicitly. Modification of 1s2p (1Po) → 1s2 (1Se) and 2p2 (3Pe) → 1s2p (3Po) transition energies under pressure are studied. Moreover, the effect of pressure on the (de)localization of electrons is studied by estimating the one- and two-electron radial moments e.g. ⟨r1⟩, ⟨r1^2⟩, ⟨r12⟩, ⟨r21^2⟩ and the
respective standard deviations. For a proper analysis of two-electron atomic data, we have estimated the positions of the one-electron thresholds.