Publication Date

2024

Document Type

Dissertation/Thesis

First Advisor

van Veenedaal, Michel

Degree Name

Ph.D. (Doctor of Philosophy)

Legacy Department

Department of Physics

Abstract

A theory to account for the ultrafast, i.e. femtosecond timescale, singlet to quintet spin crossover in divalent iron molecules is developed. The model considers an iron cluster with ligands extending in all 6 cardinal directions initially at rest in a low spin singlet ground state. An optical excitation excites an electron from the d orbitals to the ligands, changing the system from the metal centered (MC) singlet state to the metal to ligand charge transfer (MLCT) singlet state. Experimentally, it is known that the system eventually relaxes into the quintet MC state, but there are no satisfactory explanations that model the pathway and account for its ultrafast nature. This dissertation shows intermediary triplet and quintet MLCT states and establishes the importance of quantum dissipation in modeling an ultrafast transition. Vibrational modeling is used to relax energy from the system while maintaining its electronic state, while a novel damping mechanism referred to as Boltzmann damping is used to transfer weight between MLCT and MC states of the same spin multiplicity. Energy damping is shown to be the key to ensure the transition is ultrafast.

Extent

107 pages

Language

en

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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