Double Configuration Self-Consistent Field Study of the Πu1, 3Πu, 1Πg and Πg3 States of H2

Complete potential energy curves for the four lowest-lying Π states of the hydrogen molecule are calculated using an hierarchy of one- and two-configuration model wavefunctions: the Hartree–Fock model, the configuration interaction model, and the optimal double configuration model (a double configuration SCF model). Comparison and evaluation of the three models are given as a function of internuclear separation of the nuclei for the Πu1 state. An extended basis set of 10 Slater-type orbitals on each nucleus is scaled optimally for the Πu1 state; the spectroscopic constants for this state are in excellent agreement with experiment. The basis set used for the Πu1 state is employed in determining the potential energy curves for the Πu3, 1Πg, and Πg3 states; the Πu3 state shows good agreement with experiment, and the essential features for the Πg states are characterized properly.