Molecular-orbital approach to ion-atom collisions with multiply charged projectiles

In a slow collision between a multiply charged projectile ion and a neutral target atom, self-consistent molecular orbitals in the entrance channel can be defined by introducing a variational constraint which enforces the initial charge sharing and reflects the charge-equilibration process during the collision. In the present work, the interaction of an auxiliary electric field with the electronic dipole moment along the internuclear line is added to an effective single-electron Hamiltonian in order to simulate a constrained Hartree-Fock procedure. In this way, correlation diagrams for the systems N²⁺ + O and Ne⁴⁺ + Ne are computed. The diagrams exhibit crossings between energy curves of like symmetry. The correlations are found to be the same as in the corresponding charge-balanced (or neutral) systems and are hence consistent with existing experimental data.