Determination of product ions emerged from dications by varying retarding electric field in reflectron time-of-flight mass spectrometer supported by ion trajectory simulations

Abstract

Investigation of the metastable dissociations clarifies the characteristics of ionic states. Tandem mass spectrometry using an ion trap mass spectrometer, a time-of-flight mass spectrometer (TOF-MS), and the combination of those spectrometers were used for the analysis of metastable dissociation. However, investigation of the metastable dissociations of multiply charged ions is not straightforward because collision-induced charge transfer reactions to lose charges should be avoided. TOF-MS equipped with a reflectron (refTOF-MS) maintained under high vacuum condition is one of the suitable instruments. However, another difficulty arises due to the working principle of refTOF-MS: The product ions whose m/z is greater than that of multiply charged precursor ions can pass through a reflectron under the experimental conditions for detecting the product ions of a singly charged precursor ion. In this study, we report the ionization of decafluorobiphenyl (DFB) by femtosecond laser pulses and the determination of the product ions emerged from doubly charged precursor ions using a refTOF-MS. Detection of ions behind a reflectron by varying the retarding potential of a reflectron enables us to identify the m/z of product ions in two ways: measurement of the threshold retarding potential reflecting product ion; comparing the relative flight time of the product ions obtained by experiments and ion trajectory simulations. We have reported three and one metastable dissociation channels of DFB⁺ and DFB²⁺, respectively, by a conventional product ion analysis, that is the selection of a precursor ion and its product ions using an ion gate followed by the reflection and separation of them by a reflectron. In this study, we further identified the products that passed through a reflectron: charge transfer product of C²⁺; the product ion of C₄F₂²⁺ which is a secondary product of DFB ion; the product ion of DFB²⁺. The detection of the product ions that passed through a reflectron expanded the measurable m/z range of product ions emerged from doubly charged precursor ions.