Fragmentation of the POPOP molecule by electron-impact ionization

Single and dissociative ionizations of the POPOP molecule by electron impact in the gas phase are studied using mass spectroscopy. Fragmentation pathways of the molecule are proposed taking into account the common system of conjugated π-electrons and heteroatoms in the POPOP molecule. The appearance thresholds for certain fragments of the molecule are determined based on experimentally measured ionization cross sections as functions of the ionizing electron energy. An ion with m/z = 144 [C₉H₆ON]⁺ that is complementary to a fragment with m/z = 220 [C₁₃H₁₀ON]⁺ (present in the NIST mass spectrum database) is found for the first time in the mass spectrum of POPOP. Its appearance threshold is determined (E_ap = 9.48 eV). __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 482–489, July–August, 2008.