Inner-shell excitation in heteronuclear collisions. I. Orbitals and couplings in a molecular basis

The generation of a set of one-electron molecular orbitals suitable for the description of inner-shell excitation in heavy-ion-aton collisions is described. The collision of neon with oxygen is taken as an example of a slightly asymmetric (heteronuclear) collision. The adiabatic orbitals obtained from approximate Hartree-Fock solutions at varying internuclear separation exhibit avoided crossings at which the orbital character changes abruptly. These changes result in a singular behaviour of the dynamic couplings between the adiabatic orbitals. A transformation is prescribed, leading to a diabatic set of orbitals which preserve their character at crossings and between which the dynamic couplings vary smoothly with internuclear separation.