Instituto Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Phys Chem Chem Phys. 2018 Oct 17;20(40):25762-25771. doi: 10.1039/c8cp04335c.
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 (C5H5NH+), the dehydrogenated dimer (C10H9N2+) and the dehydrogenated trimer (C15H12N3+) 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.
我们报告了在 2 keV 高能电子冲击气态和凝聚相吡啶时形成的所有主要离子碎片和簇离子的直接测量结果。根据芳香环上的原子数，将母体吡啶阳离子的离子碎片分组讨论。与气态吡啶相比，由于氢迁移，凝聚态吡啶中这些组内的离子产率分布向更高质量偏移。对于吡啶，观察到了广泛的脱附氢化碎片离子和离子簇，其质量高达 320 u。质子化的母体分子 (C5H5NH+)、脱氢二聚体 (C10H9N2+) 和脱氢三聚体 (C15H12N3+) 的离子产率取决于脱附离子簇的质量。最强的簇信号归因于母体阳离子与吡啶分子亚基之间的结合。量子化学计算表明，吡啶分子与碳正离子之间形成键对于选定的簇离子的稳定性至关重要。
