Ground states of helium in exponential-cosine-screened Coulomb potentials

Ground-state energies and wavefunctions for helium atom (He) in exponential-cosine-screened Coulomb potentials (ECSCP) with screening parameter lambda, V(r) = -1/re(-lambda r) cos(lambda r) (in au), have been obtained for various values of. within the framework of Ritz's variational principle. Highly correlated and extensive wavefunctions have been used to obtain energy eigenvalues. The ground-state energies of He for various values of lambda have been shown to converge with the increase of the terms in the wavefunction. The ground-state energies of He+ along with the ionization potentials of He have also been reported. Our present work represents a first calculation, for the first time in the literature, of the ground-state energies of He interacting with ECSCP.