STRATEGY FOR AN EVALUATION OF CORE EXCITATION-ENERGIES IN COMPLEX-MOLECULES - APPLICATION TO SF6

Modelling of single core-hole states is proposed, which consists of ad ding an external charge exerting on the remaining electrons to an oute r repulsion globally equivalent to the inner attraction resulting from the partial unscreening of the nucleus, For a given complex molecule and an ionized core level, this outer equivalent charge (oech), which may be fractional, can be computed by comparing results from exact cor e-hole calculations and from applying Koopmans' theorem to valence-ion results for a related simpler molecule. For double core-hole states, the total relaxation energy is computed by adding to the single relaxa tion energies an induced relaxation energy approximated by the geometr ic average of the former. This model helps to assign two satellites in the photoelectron spectrum of SF6 to singlet and triplet double core- hole states.