Coherent vibrational and dissociation dynamics of polyatomic radical cations

The ultrafast dynamics of polyatomic radical cat- ions contribute to important processes including energy transfer in photovoltaics, electron transfer in photocataly- sis, radiation-induced DNA damage, and chemical reac- tions in the upper atmosphere and space. Probing these dynamics in the gas phase is challenging due to the rapid dissociation of polyatomic radical cations following elec- tron removal, which arises from excess electronic excita- tion of the molecule during the ionization process. This Concept article introduces the reader to how the pump- probe technique of femtosecond time-resolved mass spectrometry (FTRMS) can overcome this challenge to capture coherent vibrational dynamics on the femtosec- ond timescale in polyatomic radical cations and enable the analysis of their dissociation pathways. Examples of FTRMS applied to three families of polyatomic radical cat- ions are discussed