Investigations of Higher Order Multipole Effects within the Context of Quantum Electrodynamics

Frost, James (2022) Investigations of Higher Order Multipole Effects within the Context of Quantum Electrodynamics. Doctoral thesis, University of East Anglia.

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It has been known for some time that effects of terms of a higher order than the dipole can have a strong influence on the rate and efficiency of energy transfer in some systems. This led to an initial desire to investigate and understand the impact of higher order multipole terms in resonance energy transfer (RET). Towards that objective this thesis presents three different computational models developed in order to investigate such effects. In chapter two, a computational analysis of the quantum electrodynamical (QED) coupling profiles between a pair of J-aggregate dye molecules is presented. Two sets of calculations were carried out: one with and one without the inclusion of the next term beyond the dipole in the multipole expansion, namely the transition quadrupole moment. The results indicate that in some relative orientations the quadrupole terms could play an important role in accurately describing the RET process. Having explored the influence of the transition quadrupole moment computationally on a physical system, the subsequent two chapters are much more fundamental in nature, looking to analyse the characteristics of the transitions governed by a quadrupole as well as the moment itself in more detail. This is achieved through an examination of the emitted electromagnetic fields. In chapter three a novel application is produced to examine the electric field structure through its phase for dipole and quadrupole transitions in the hydrogen atom. These results provide pictorial insights into how angular momentum (AM) associated with a photon is encapsulated in the electric field. This work led to a desire to consider similar processes using an alternative picture, namely by considering spherical fields generated using vector spherical harmonics (VSHs) in a methodology dubbed the spherical wave (SW) approach. In chapter four, an extensive analysis of the SW approach was carried out in order to create a sophisticated piece of software that was developed and the results related to previously derived analytical solutions. The new computational program offers significant new insight that addresses some of the nuances raised in chapter three. These new computational approaches provide opportunities to garner new insights into multipolar processes and address both fundamental and practical questions in optics and chemical physics.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Chemistry
Depositing User: Nicola Veasy
Date Deposited: 01 Dec 2022 11:10
Last Modified: 01 Dec 2022 11:10


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