MEASURED AND CALCULATED DOUBLE-IONIZATION ENERGIES OF 2-HALOETHANOLS

Double-charge-transfer spectroscopy was used to measure the double-ion ization energies of the 2-haloethanols FCH2CH2OH, ClCH2CH2OH, BrCH2CH2 OH and ICH2CH20H; the values obtained were 30.1 +/- 0.5, 28.1 +/- 0.5, 27.6 +/- 0.5 and 26.9 +/- 0.5 eV, respectively. In addition, the ener gies were calculated using ab initio methods and the GAUSSIAN 90 progr am package. The measured and calculated values for FCH2CH2OH are in ag reement, but for the three other molecules the calculated values are s ignificantly lower than those measured. The discrepancies in the calcu lations are due mainly to the underestimation of correlation energies by the appropriate MP2 method, which becomes progressively worse with increasing number of electrons in the system.