Development of Ion Momentum Imaging for Reaction Control Using Ultrafast Charge Migration Processes

Abstract

Multi-fragment momentum imaging methods in which the momentum images of all kinds of fragment ions can be captured simultaneously, are developed for controlling chemical reactions through ultrafast charge migration processes of polyatomic molecules, including amino acids or bio-relevant molecules. In the momentum imaging method developed in this study, the temporal information of the fragment ions is recovered using time-intensity or time-polarization tagging methods, where the polarization of fluorescence emitted from the phosphor is temporally modulated by an electro-optic light modulator. This realizes one-to-one correspondence between the time-of-flight of fragment ions and the polarization direction of fluorescence. In addition, an ion momentum imaging apparatus with multi-fragment momentum imaging is integrated with a sample injection system of non-volatile molecules through laser-induced acoustic desorption. The operation modes can be easily switched from the velocity map imaging to spatial map imaging to measure the spatial-resolved mass spectrum in a single-shot.