Pair-function calculations for two-electron systems in model plasma environments.

The pair-function formalism has been extended to the calculation of atomic and ionic properties in plasma environments that are modeled in terms of analytic screening potentials of the usual Debye form and the more general Debye-Laughton type. The theory has been applied to two-electron systems. As particular applications, the stability of H{sup {minus}} and the energy splitting of several 1{ital sns} and 1{ital snp} states of the He atom have been studied in model plasma environments as well as the energies of allowed and forbidden transitions.