Long- and intermediate-range interaction between hydrogen atoms in the B 1Σ/sub u/+ state

Abstract The energy of the hydrogen molecule in the B 1 Σ state, for internuclear separations 12 ≦ R ≦ 20 a.u., has been computed using an 80‐term variational wave function depending explicitly on the interelectronic distance. The same type of wave function has been employed in the perturbation theory approach. Using the polarization approximation, and not expanding the interaction Hamiltonian, the first‐, second‐ and third‐order energies have been computed and higher‐order corrections have been estimated. The results show that in the region under consideration E and E represent the dominant contributions to the interaction energy in the B state.