Implementation of cryogenic techniques for the investigation of ion-neutral reactions in the cold regime

'Cold' chemistry, that is, chemistry conducted below 1K, is an exciting and rapidly expanding field with the potential to enhance our understanding of low temperature reaction dynamics. This is a regime where the quantum nature of the reaction is expected to play an increasingly important role. Through studying this domain, we can develop a better understanding of the reaction dynamics in the coldest parts of the universe and answer problems such as the enhanced abundance of cosmic deuterium compared to the abundance in the Interstellar medium (deuterium fractionation). It will also allow us to test many theories proposed to predict patters of reactivity in this cold regime, theories that were proposed many decades ago and remain to be tested experimentally. Validation or improvement of these theories will be invaluable to the field of chemical reaction dynamics and will enable a completely novel analysis that has not been previously possible. Specifically, I will start my studies by trying to create an internally cold source of oriented ammonia (ND3) molecules using our buffer gas apparatus that is connected to a quadrupole velocity guide. A cold beam has successfully been produced with this apparatus in the past, but the vast majority of molecular orientation is lost once the beam passes through a region of zero electric field after the guide exit. Applying a field to this region (or redesigning the post-guide segment of the apparatus) will help to retain a much larger percentage of this orientation. A linear Paul ion trap is connected to the guide exit which provides us with a way of producing a translationally cold source of ions via either laser or sympathetic cooling. Connecting these two sources of cold reactants will allow us to study the effect of low temperature and molecular orientation on the rates of reaction. Further research will be by way of a new, cryogenic ion trap which is currently being developed. The goal is to attach this to the Zeeman decelerator which will provide a source of cold radicals. Using the Zeeman decelerator we will be able investigate the reactivity of radical neutral species with laser and sympathetically cooled ions which are trapped in the cryogenic ion trap. These two methods allow us to investigate the reactivity of a wide range of reactants and probe the cold regime even further than has been possible before.

This project falls within the EPSRC 'Chemical Reaction Dynamics and Mechanisms' research area and will provide a novel methodology for the study of ion-molecule reactions which will align us with the EPSRCs strategic goals of establishing the UK as a world leader in this field. The techniques are of interest to both the physics and chemistry fields and will have links to many other EPSRC research areas such as 'Computational and Theoretical Chemistry' and 'Cold Atoms and Molecules', making this project of wide interest to the EPSRC and the physical chemistry community as a whole.