Atomic and molecular applications of open-shell cluster expansion techniques with incomplete model spaces

Abstract

Pilot numerical applications are reported of two recently formulated cluster expansion formalisms that generate connected effective Hamiltonians even for incomplete model spaces. Results are presented for prototype systems such as (a) the He atom, (b) the H₂ molecule and (c) the He₂²⁺ ion. For He and H₂ we give results for typical examples of incomplete model spaces, and for He₂²⁺ we present adiabatic potential energy curves the first four ¹Σ_g⁺ and the first two ³Σ_g⁺states, calculated with an incomplete model space.