Unravelling stereodynamic effects in the scattering of NO(X)

Thesis

If humanity is to truly master chemistry, it must be able to understand the processes linking reactants to products. One way to exert control over collisional chemical reactions is by having the ability to choose the geometry of the reactants before the collision. Hence, it is vital that significant study is put into theoretical and experimental work in the field of stereodynamics that can facilitate the prediction of the effects of this control. Here, work is presented which aims to further this cause through studies of inelastic scattering of the molecule NO(X), which uses electric and magnetic fields to orient either one or both collision partners before the collision.

On the experimental side, progress towards an experiment in which NO(X, j =1/2f) collides with a symmetric top molecule, such as ND₃ or CH₃F, in a specific quantum state in conditions in which both molecules are oriented by a single electric field. This experiment will make use of the double hexapole which has been designed and tested, with those results presented here. Theory to understand how these molecules may orient in an electric field strong enough to orient NO(X, j = 1/2f) is also shown. New data analysis methods are also discussed which may be used to extract stereodynamic quantities from 3D velocity map imaging scattering data, the format in which experimental data will be collected when studying the NO(X) + symmetric top molecule system.

Two studies are also shown which look closely at the theory behind these stereodynamic effects, allowing characterisation. This theory is first displayed by using electric fields to orient a ²Π molecule (such as NO(X)) in a collision with a rare gas atom, or an unoriented molecule, with some examples shown to display the power of the formalism and the insights it can provide. After this, the theory is expanded to a system in which a ²Π molecule is oriented by an electric field and it collides with another molecule whose angular momentum is oriented by a magnetic field. Quantum mechanical scattering calculations are then presented to illustrate the utility of this theory, helping to provide insights into the potential energy surfaces involved in the scattering and the properties of resonances seen in low energy scattering.

Authors: McCrea, M

• DOI: 10.5287/ora-yrd7x2je6
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: reaction dynamics; molecular orientation; stereodynamics; inelastic scattering