Identification of the electronic transitions in the double ionization of six amines to singlet electronic states of their dications

Abstract The double-ionization energies of methylamine, dimethylamine, trimethylamine, ethylamine, propylamine and butylamine were measured and calculated. Transitions to singlet states of the ions were considered in order to complement the previously obtained information on transitions to triplet states. The double-ionization energies were determined experimentally from the positions of peaks observed in double-charge-transfer spectra. Information on the electronic transitions giving rise to the peaks was obtained by comparing the measured energies with those calculated using a semi-empirical form of the multiple-scattering Xα computational method. It was shown that for some of the dications the density of states is high. An ab-initio computational method, used with the 3-21G and 6-31G ∗ basis sets, predicted quite accurately the trend in the lowest double-ionization energies measured.