Unified description of chemical bonding in H2 isotopomers, including Ps2, μ2 and bi-excitons

We developed an unified treatment of the low-lying states of the general A+A+e−e− systems based on the concepts of chemical bonding, using an intuitive valence bond electronic wavefunction. A reduced mass correction accounts for the effects of the finite masses of nuclei A. The potential energy curves, the electronic densities and the ionic contribution show similar behaviour for all systems. The number of vibrational states versus the mass relation λ is obtained and compared to theoretical predictions. We verified that the use of atomic masses instead of nuclear masses is fundamental in order to obtain the only bound state in the cases λ≃1.