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Title: Diffusion kinetics in radiation chemistry : an investigation of competition and correlation effects
Author: Al-Samra, Eyad H.
ISNI:       0000 0004 6353 1204
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2015
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The study of radiation chemistry is very important because of the wide range of applications. Many of the processes in radiation chemistry evolve randomly and can be modeled using the theory of stochastic process. The main aim of this thesis is to study correlation effects in model systems of the type found in radiation chemistry, i.e. clusters of reactive particles. Studies of this type involve a substantial amount of computer simulation. The first work described in the thesis shows how the Message Passing Interface can be incorporated in the algorithms used to simulate radiation chemical kinetics and how that can improve the performance of the programs. The reaction probability for two diffusing particles is well known, and current theories are based on this, making the approximation that pair distances evolve independently. This work analyses some correlation effects that appear in a system of three particles, with some new results, notably in the distribution of the joint distribution of the distances and the underlying 3-body backward diffusion equation, but it has not yet been possible to use these results to introduce corrections in the working simulations. The competition between scavenging and recombination is investigated in detail in chapters 4-6. A correction to the Smoluchowski theory for a fully-diffusion controlled reaction is proposed, and it is shown how the Independent Reaction Times method can be used to simulate this competition. The approximation is justified both by comparison to simulation results and theoretically, and is shown to apply to all the ordered scavenging reactions in a multi-particle system. Finally, the problem of modeling a reversible reaction is briefly investigated in chapter 7. The main result of this chapter is a generalization of previous work on the distance between a pair conditional on its future reaction time, generalized to a radiation boundary condition.
Supervisor: Green, Nicholas Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available