Ion-radical reactions relevant to the interstellar medium and outer atmosphere, under cold controlled collisions

This project falls within the EPSRC Physical Sciences theme, with particular relevance to the Analytical Science, Chemical Reaction Dynamics and Mechanisms and Cold Atoms and Molecules research areas. The primary objective of this project is to study ion-radical reactions under extreme conditions, by combining a Zeeman decelerator and a cryogenic ion-trap. Ions and radicals are highly reactive species, therefore their reactions are frequently really challenging to study precisely. Indeed, the presence of other competing reaction channels typically complicates (or, in some cases, even prevents) the study of target reactions. By overcoming this challenge, we will be able to obtain reaction rates for many ion-radical reactions relevant to interstellar medium or outer atmosphere, that are yet to be experimentally measured. These data are of great interest for validating theoreticians' models of reactions in such media. In order to achieve this objectives, I will develop and characterise a novel experimental set-up to study ion-radical reactions in gas phase. We already have a source of cold and controlled radical species provided by a Zeeman decelerator and a magnetic guide. This source of cold radicals will not only quantum-state select radical species of interest, but also tune and filter their velocities. We will combine a cryogenic ion-trap to the source of cold radicals. This cryogenic ion trap will be cryogenically cooled to less than 10 K to reduce the black body radiation and therefore to lower the internal temperature of molecular ions. I am in the process of constructing this new cryogenic ion trap. The device is also equipped with a vibration-isolation system and an imaging detection method
will be combined with mass spectroscopy detection capabilities. To handle a more efficient, compact design of the ion trap, a new optical imaging system has been developed. The resulting instrument will enable us to study reactions between ions and radicals with unprecedented control over the reaction parameters. We will be able to study these reaction systems with exceptional sensitivity, as we can monitor the reactions of single ions. No other instrument combines a cryogenic ion trapping environment with optical access, mass spectrometry detection capabilities, and a source of cold radical reactants.