ELECTRONIC-STATE ENERGIES OF THE CH2I22+, CHI32+ AND CL42+ DICATIONS

The double-ionization energies of CH2I2, CHI3 and Cl4 have been measured and calculated. Double-charge-transfer spectrometry was used in the experimental part of the investigation, and a modified multiple scattering Xalpha method was used to calculate the energies. In order to test the accuracy of the calculations, the computational method was initially applied to CH3I; the values obtained were found to be in good agreement with those measured previously. Calculated data for CH2I2 indicate that a large number of electronic states of the dication exist. By forming appropriate groups of states, mean calculated double-ionization energies were obtained which agree with the measured data. For CHI3 and Cl4, the number of states calculated to exist is considerably less. When groups need to be formed, the numbers in them are much less than those for CH2I2. Good agreement between grouped calculated data and those measured was obtained for CHI3 ard Cl4. The exception was the four lowest states of CI42+, which appear not to be populated experimentally. A probable explanation is that the endoergicities of the relevant double-electron-capture reactions are too low, lying outside the operative reaction window of endoergicities.