Excited-state dynamics of gas-phase ions

James N. Bull

School of Chemistry, University of East Anglia, Norwich, United Kingdom

Action spectroscopy, usually performed in the gas phase, encompasses a family of spectroscopic techniques that monitor the “actions” induced when molecules absorb light. These actions include electron ejection (photoelectron and photodetachment spectroscopy), molecular fragmentation (photodissociation spectroscopy), and isomerisation or structural rearrangement (photoisomerisation spectroscopy). Our laboratory develops action-spectroscopy instrumentation and methodologies in both the frequency and time domains, employing ultrafast laser systems to probe excited-state dynamics. We focus on uncovering the behaviour and function of photoactive biological chromophores, molecular photoswitches for technological applications, and astrochemically relevant species whose excited-state mechanisms underlie their interstellar resilience. A key theme is the concerted applciaiotn of several action spectroscopy techniques, such as coupling ion mobility for isomer selection with photoelectron velocity-map imaging and time-resolved measurements, to build a comprehensive picture of the underlying potential energy surfaces.