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The application of quantum electrodynamics to intermolecular interactions

Jenkins, Jonathan Kingsley; (1991) The application of quantum electrodynamics to intermolecular interactions. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

Molecular quantum electrodynamics describes the interaction of molecules with radiation. This theory in its multipolar form is applied to intermolecular interactions; coupling proceeds through the radiation field and is mediated by an exchange of photons. The basic theory is outlined in Chapter 1 and the conventional transformation from the minimal-coupling to the multipolar Hamiltonian is generalized to include non-neutral systems and translational motion. The equivalence of the multipolar and minimal-coupling forms is demonstrated by comparison of results obtained for two-photon absorption and scattering by chiral molecules. Chapter 4 examines the dispersion interaction between neutral molecules; all interactions occur via the field and are fully retarded. The standard result in terms of electric-dipole polarizabilities is supplemented by those obtained through interaction of higher-order molecular multipole moments with the field; electric-quadrupole and magnetic-dipole interactions are included. The results are valid at all separations large enough to neglect electron exchange and apply to molecules with specific orientations. Rotationally-averaged expressions are presented also, as are results obtained in the near- and far-zones. Where appropriate results have been expressed in terms of pure electric and mixed electric-magnetic polarizability tensors. The Hamiltonian developed in Chapter 2 is applied in Chapter 5 to the calculation of the dispersion interaction between a molecule and an ion at rest; supplementing the energy shifts calculated in Chapter 4 are non-retarded terms arising from charge-multipole - 6 interactions. All terms up to a cut-off point of an R-6 dependence on separation are taken into account and the minimal-coupling treatment of this interaction is contrasted. In the final chapter the theory is modified in order to determine the interaction of a free electron with a neutral molecule. A new transformation to the minimal-coupling Lagrangian is used where only the molecular terms are transformed; the dynamics of the free electron are described within the minimal-coupling formalism while the multipolar nature of the molecular interactions is preserved.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: The application of quantum electrodynamics to intermolecular interactions
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
URI: https://discovery.ucl.ac.uk/id/eprint/10124696
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