Charge Transfer and Metastable Ion Dissociation of Multiply Charged Molecular Cations Observed by Using Reflectron Time-of-Flight Mass Spectrometry

Abstract

A multiply charged molecule expands the range of a mass window and is utilized as a precursor to provide rich sequence coverage; however, reflectron time-of-flight mass spectrometer has not been well applied to the product ion analysis of multiply charged precursor ions. Here, we demonstrate that the range of the mass-to-charge ratio of measurable product ions is limited in the cases of multiply charged precursor ions. We choose C₆ F₆ as a model molecule to investigate the reactions of multiply charged molecular cations formed in intense femtosecond laser fields. Measurements of the time-of-flight spectrum of C₆ F₆ by changing the potential applied to the reflectron, combined with simulation of the ion trajectory, can identify the species detected behind the reflectron as the neutral species and/or ions formed by the collisional charge transfer. Moreover, the metastable ion dissociations of doubly and triply charged C₆ F₆ are identified. The detection of product ions in this manner can diminish interference by the precursor ion. Moreover, it does not need precursor ion separation before product ion analysis. These advantages would expand the capability of mass spectrometry to obtain information about metastable ion dissociation of multiply charged species.

Keywords: femtosecond laser; ion trajectory simulation; mass spectrometry; reflectron; tunnel ionization.