EXPERIMENTALLY DETERMINED AND CALCULATED VALUES OF THE ENERGIES REQUIRED TO FORM DOUBLY CHARGED IONS OF THE BROMOMETHANES CH3BR, CH2BR2 AND CHBR3

Two experimental techniques were used to determine the double ionization energies of CH3Br, CH2Br2 and CHBr3. In one, these energies were measured directly by double‐charge‐transfer spectroscopy. In the other, charge stripping of [CH3Br]+, [CH2Br2]+ and [CHBr3]+ ions was investigated and the ionization energies of the singly charged ions were measured. The double ionization energies of the molecules obtained by adding known single ionization energies of the molecules to the single ionization energies of the ions were in good agreement with those determined by double‐charge‐transfer spectroscopy. The relevant mean values from the two techniques were 28.9 ± 0.5, 27.5 ± 0.5 and 29.1 ± 0.5 eV for the double ionization energy of CH3Br, CH2Br2 and CHBr3, respectively. The results of ab initio calculations using second‐order Møller‐Plesset perturbation theory were in good agreement with the observed double ionization energies; they were consistently slightly lower than the experimental values. Copyright © 1990 John Wiley & Sons, Ltd.