FULL GEOMETRY OPTIMIZATIONS OF CORE IONIZED SPECIES AND THEIR EQUIVALENT CORE IONS - AN AB-INITIO STUDY OF ENERGIES, GEOMETRIES, CHARGES AND VIBRATIONAL FREQUENCIES

Full geometry optimizations have been performed on the C1s and O1s core ionized states of ethanal and on the corresponding equivalent core ions using ab initio 6-31G* Hartree-Fock SCF calculations. The good agreement between the calculated properties of the core hole and equivalent core ions provides further justification for the use of the equivalent cores approximation for calculating properties of core ionized species. Exceptions to the excellent geometry predictions observed in ethanol occurred in two cases where stereochemically significant lone pairs were present.