Fragment and cluster ions from gaseous and condensed pyridine produced under electron impact. Issue 40 (4th October 2018)

• Record Type: Journal Article
• Authors: Ribeiro, Fabio de A.; Rudek, Benedikt; Cerqueira, Henrique B. A.; Oliveira, Ricardo R.; Rocha, Alexandre B.; Rocco, Maria Luiza M.; Wolff, Wania
• Is Part Of: Physical chemistry chemical physics. Volume 20:Issue 40(2018)
• Page Start: 25762
• Page End: 25771
• Publication Date: 2018-10-04
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c8cp04335c
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : The ion-distribution from condensed pyridine due to 2 keV electron impact shows hydrogenated fragments and clusters with m / z ≤ 320 u and shifts towards higher masses compared to the gas-phase fragmentation. The formation of a bond between the pyridine and a carbenium ion is crucial for the stability of the selected cluster ions. Abstract : We report on direct measurement of all major ion-fragments and cluster-ions formed during high-energy electron impact of 2 keV on gaseous and condensed-phase pyridine. The ion-fragments of the parent pyridine cation are discussed in groups according to the number of atoms from the aromatic ring. The ion yield distributions within these groups show significant shifts towards higher masses for condensed pyridine compared to gaseous pyridine due to hydrogen migration. A wide spectrum of desorbed hydrogenated fragment-ions and ionic clusters with masses up to 320 u are observed for pyridine. The ion yields for the protonated parent molecule (C5 H5 NH + ), the dehydrogenated dimer (C10 H9 N2 + ) and the dehydrogenated trimer (C15 H12 N3 + ) depend on the mass of the desorbing ionic clusters. The strongest cluster signals are assigned to binding between the parent cation and subunits of the pyridine molecule. Quantum-chemical calculations reveal that the formation of a bond between the pyridine molecules and a carbenium ion is crucial for the stability of selected cluster ions.