Development of an ion trap with a metastable atom bombardment ionization source to observe ion-molecule reactions

Abstract

An ion trap/time-of-flight mass spectrometer equipped with a metastable atom bombardment (MAB) ionization source was constructed in order to observe ion-molecule reactions controlled by the internal energy of ions. In the MAB source, the internal energy of the generated ions was controlled by using different rare gases. Moreover, the constructed device was used to analyze ion-molecule reactions of the p-xylene cation and its dissociation ions with p-xylene. It was found that the reaction afforded a single product without any structural isomers, which could then be easily analyzed. An abundant amount of [M]+ (m/z 106, C8H10+) and trace levels of dissociation products were observed in the Kr MAB ionization, while in the Ar MAB ionization, [M−CH3]+, [M−H]+ (m/z 105, C8H9+), and [M+CH]+ (m/z 119, C9H11+) ions were generated in addition to the molecular ion. Moreover, investigating the production routes to [M−H]+ and [M+CH]+ ions using a resonance ejection method in the ion trap indicating that generation of these ions was related to the hydride transfer reaction of C7H7+ with p-xylene. Results from the calculations of the reaction profile of this transfer using the density functional theory (DFT) method supported the experimental results.