Auger spectra of linear alkynes and alkenes. Experiment and theory

Abstract

The Auger spectra of molecules in the two sequences 1-propyne, 1-butyne, 1-pentyne and 1-propene, 1-butene, 1-pentene have been studied in a comparative way. Experimental Auger spectra are reported for 1-propene, 1-butene and 1-pentyne. Two-particle Green's function calculations interpret these spectra and make predictions for the other members of the studied sequences. The calculated Auger spectra are related to ionization spectra by a renormalization technique. The ionization potentials display the formation of the 2s bands of the alkyl chain in both sequences which is confirmed by the experimental valence XPS spectra. The 2p regions show influence of hyperconjugation between the multiple bond and the alkyl group. From atomwise decomposed theoretical Auger spectra it is observed that the sp 2 pattern of the double bonds appears for both terminal carbon atoms of the alkenes, but that the sp pattern of the triple bond appears only for one terminal carbon atom, the second one already having a distorted lineshape. The sp 3 patterns of the methyl and methylene units in the alkyl group are distorted throughout the chain with some oscillations of maxima with the atomic position.