Electronically excited states of the CH3I2+ ion

Abstract

A double-charge-transfer spectroscopy study has provided evidence for the existence of four low-lying electronic states of the CH₃I²⁺ ion, the double-ionization energies to which are 27.0 ± 0.3, 29.6 ± 0.3, 31.3 ± 0.5 and 36.5 ± 0.5 eV. Three of these energies agree, within experimental error, with those determined previously in a dissociative double photoionization study of CH₃I. The present investigation reveals for the first time the state at 29.6 eV. The value of the double-ionization energy to the ground triplet state, calculated in the present investigation using the single-determinant Hartree–Fock approximation to the many-electron wavefunction with corrections of second-order Møller–Plesset perturbation theory for correlation effects, is 25.80 eV, somewhat lower than the measured value of 27.0 eV.