A comparative study of two-electron systems with screened Coulomb potentials

The one-electron potentials specifically considered are: v(r)=vC(r)=−1rCoulombvD(r)=−1rexp(−λr)Debye (Yukawa)vHu(r)=−λexp(λr)−1HulthénvECSC(r)=−1rexp(−λr)cos(λr)ECSC∗,∗Exponential-Cosine-Screened-Coulombwhere λ is the screening parameter. For each of the λ-dependent potentials we compare one- and two-electron spectra corresponding to distinct values of λ. This is followed by pairwise comparison of distinct potentials.