Taming the reaction dynamics of paramagnetic species
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 proposal, I provide a solution. I will develop 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 an effusive 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. We will examine important gas-phase reactions involving radicals in isolation (i.e. without competing side reactions) for the first time. 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.