DOUBLE-IONIZATION ENERGIES OF THE CHLOROETHANE MOLECULES CH3CH2CL, CH3CHCL2, CH3CCL3, CH2CLCH2CL, CH2CLCHCL2, CH2CLCCL3, CHCL2CHCL2, CHCL2CCL3 AND CCL3CCL3

Double-ionization energies of the molecules listed in the title were measured by double-charge-transfer spectroscopy. Since spin is expected to be conserved in double-electron-capture reactions, and OH+ was used as the projectile ion, the lowest energies measured should correspond to ground triplet states of the dications. Double-ionization energies to these states were calculated using the GAUSSIAN 86 ab initio program package at the Hartree-Fock level with second-order Moller-Plesset perturbation theory. The measured double-ionization energy of CH3CH2Cl is 29.8 +/- 0.5 eV but the corresponding energies for all the other molecules are lower, lying within +/- 0.7 eV of 28.1 eV. A similar pattern is seen in the calculated data. The measured energies are in general higher than those calculated but in all cases by not more than 5%. Double-ionization energies for the fluorine analogues were also calculated and are compared with previously published measured data.