Ritz variational calculation for the singly excited states of compressed two-electron atoms

摘要

A detailed analysis on the effect of spherical impenetrable confinement on the structural properties of two-electron ions in S- states has been performed. The energy values of 1sns [n=2-4] (S-3(e)) states of helium-like ions (Z=1-5) are estimated within the framework of Ritz variational method using explicitly correlated Hylleraas-type basis sets. The correlated wave functions used here are consistent with the finite boundary conditions due to spherical confinement. A comparative study between the singlet and triplet states originating from a particular electronic configuration shows incidental degeneracy and the subsequent level-crossing phenomena. The thermodynamic pressure felt by the ion inside the sphere pushes the energy levels toward continuum. Critical pressures for the transition to strong confinement regime (where the singly excited two-electron energy levels cross the corresponding one-electron threshold) as well as for the complete destabilization are also estimated.