Investigating molecular fragmentation mechanisms and the kinetic energy distributions of fragments can offer crucial insights into their roles in plasma physics, radiation-induced damage in biological tissues, and interstellar chemistry. In this study, we conduct the experiments on collision between 3 keV/u \rm Ar^8+ ions and CH₃F molecules by using a cold target recoil ion momentum spectrometer (COLTRIMS).

We focus on the three-body fragmentation channel H⁺+ \mathrmC\mathrmH_2^+ +F⁺ resulting from C—F and C—H bond cleavage in CH₃F³⁺ ions, and measure the three-dimensional momentum vectors of all fragment ions. The fragmentation mechanism involved is analyzed using ion-ion kinetic energy correlation spectra, Newton diagrams, Dalitz plots, and other correlation spectra.

Our results reveal two different dissociation mechanisms for the H⁺+ \mathrmC\mathrmH_2^+ +F⁺ channel, i.e. concerted fragmentation and sequential fragmentation, with the former one being dominant. In the sequential fragmentation process, H⁺ and the intermediate CH₂F²⁺ are firstly formed, followed by further fragmentation of the intermediates into \mathrmC\mathrmH_2^+ and F⁺. No sequential pathways involving HF²⁺ or \mathrmC\mathrmH_3^2+ intermediates are identified. Furthermore, we observe two types of concerted fragmentation processes with different dynamical characteristics, suggesting that hydrogen atoms in CH₃F³⁺ may occupy different chemical environments. This phenomenon can originate from either molecular isomerization producing different structural geometries or the Jahn-Teller effect leading to inequivalent C—H bonds. This study reveals the three-body dissociation dynamics of CH₃F³⁺ induced by highly charged ion collisions, highlighting the significant role of the Jahn-Teller effect or molecular isomerization in the ionic dissociation of polyatomic molecules.