Double ionization of the n-alkyl iodides C2H5I, C3H7I and C4H9I

Abstract

Double ionization of C₂H₅I, n-C₃H₇I and n-C₄H₉I has been investigated experimentally using double-charge-transfer spectroscopy. On the assumption that spin is conserved in the double-electron-capture reactions, and because of the use of OH⁺ as the projectile ion, it is probable that triplet states of the dications were populated. Peaks in the spectra were interpreted in terms of the electronic transitions giving rise to double-ionization energies calculated using a semi-empirical version of the multiple scattering Xα(MSXα) method of molecular orbital calculations. The density of states was found to increase as the alkyl chain-length increased, and most of the peaks observed were interpreted as being due to transitions to groups of close-lying states. In addition to the use of the MSXα method, ab initio double-ionization energies to the lowest triplet states of the dications were calculated.