Periodic Reporting for period 4 - RadiCool (Taming the reaction dynamics of paramagnetic species)
Okres sprawozdawczy: 2024-01-01 do 2025-06-30
Radicals are paramagnetic species---atoms or molecules with an unpaired electron---and they are prevalent in gas-phase environments such as the atmosphere, combustion systems and the interstellar medium. In spite of their real-world importance, very few experimental methods can be applied to the precise study of gas-phase radical reactions. This is primarily due to the significant challenges associated with such studies; there are no established methods for generating a pure beam of atomic or molecular gas-phase radicals with tuneable properties. In this project, we provide a solution. We are developing a versatile and innovative “magnetic guide”, for the generation of a pure and state-selected beam of radicals. The magnetic guide will feature a series of specially-designed permanent magnets (Halbach arrays) and skimming blades. It will act as a stand-alone device, producing a pure beam of radicals with continuously tuneable velocity from a gas mixture (containing radicals, precursor molecules and seed gases). The magnetic guide will be combined with two existing experiments---an ion trap and a liquid-surface set-up---and will enable us to study ion-radical and radical-liquid surface interactions with unprecedented control and precision. Our measurements will provide the missing experimental data needed to improve the accuracy of (for example) complex atmospheric chemistry models---replacing untested predictions from capture theory calculations.
A key element of this project is the development of a new magnetic guide device. A second-generation magnetic guide has been successfully designed, constructed, and characterised. This work was recently presented at a scientific meeting (International Symposium on Molecular Beams, Crete, June 2023) and is being prepared for publication. Other achievements related to the project include: the development and publication of a full three-dimensional self-consistent mean field DSMC (SCMFD) code; the formation of Coulomb crystals in the cryogenic ion trap; the optimisation of a Zeeman-decelerated and magnetic-guided radical beam; and the study of new reaction systems within Coulomb crystals.
The new magnetic guide device represents an exciting development in the control of molecular radical beams. We anticipate that we will be able to push beyond the current state-of-the-art by manipulating the internal energy distribution, the velocity, and the purity of radical beams. Following these final characterisation studies, we will use these radical beams to study ion-radical and radical-liquid surface interactions.