The eigenspectrum of the relativistic two-center Hamiltonian in the diatomic basis of bound hydrogenlike Dirac-spinors

During heavy ion collisions below the Coulomb barrier adiabatic molecular orbitals are formed for the inner electrons. For systems with total changes exceending Z=Z₁ + Z₂ 60 relativistic effects are important and we, therefore, use the two-center Dirac Hamiltonian to describe the dynamics. We investigate the method to approximate these molecular orbitals by an expansion in a di-atomic basis of Dirac wave functions and determine the binding energies by a variation of the expansion coefficients. Deviations from adiabaticity are taken into account to first order in the relative velocityv/c 0.1) of the nuclei which is considerably smaller than the electron velocity.