Effect of Mass Polarization on Bound and Resonance States of Two-Electron Systems

Pioneering calculation is done to evaluate the resonance parameters (position and width) for the first four 1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$<^>1$$\end{document}Se\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$<^>e$$\end{document} resonance states of He iso-electronic ions (Z=2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$Z= 2$$\end{document}-6, Z is the nuclear charge) by including mass polarization term. The state-of-the-art stabilization method in the framework of explicitly correlated multi-exponent Hylleraas basis set is employed for the evaluation of resonance parameters. Within the purview of Ritz variational method, the present wavefunction can produce bound state energies for 1sns states (n=1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$n= 1$$\end{document}-6, n being the principal quantum number) of the He iso-electronic sequence. The estimated energy values for bound states are in fair agreement with the results obtained by adopting other theoretical methods, thereby providing a testing ground for the present methodology. An in-depth analysis reveals that the effect of mass polarization remains nearly the same for all the bound states, whereas it diminishes notably as the nuclear mass of the systems increases. On the other end, for a specific resonance state, the influence of mass polarization on the resonance parameters becomes much more significant for heavier ions.