Electron nuclear dynamics: Resolution of electronic states, extension to direct ionization, and the irradiation of biomolecules in proton cancer therapy
Privett, Austin J.
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The research presented in this dissertation develops along three fronts: (1) the development and improvement of theoretical methods to use within the framework of time-dependent many-body quantum mechanics at the atomic and molecular levels, (2) the implementation of those developments in computer code, and (3) the application of that computer code to the study of molecular processes. The bulk of the studied molecular processes are important for understanding the effect of proton radiation on human tissues and its use in the context of cancer treatment. The dissertation begins in Chapter 1 with an introduction to the motivating scientific application---proton cancer therapy---of the computational work I have done throughout the course of my PhD studies. This is followed by a description of the theoretical tools (primarily END, the Electron Nuclear Dynamics theory) used to investigate related scientific questions in Chapter 2. After this introductory material, the reader will find in Chapter 3 some of the more practical methodological and software developments I have contributed which have helped the computational investigation and are implemented in the code PACE (Python Accelerated Coherent-states Electron nuclear dynamics). After the presentation of these details, Chapters 4 and 5 show the results of my investigation of proton collisions on two systems important for proton cancer therapy: DNA/RNA nucleobases and water clusters. After piecing together information learned up to that point in my research, I raised possible solutions to unanswered questions concerning the applicability of END to (1) spin symmetry-breaking processes, and (2) collision energies above the ionization threshold, an energy region previously assumed to be out of reach for accurate END simulations. It could be said that these developments improved the performance of END at (1) low energies and (2) high energies. Investigations of these possible solutions are described in Chapters 6 and 7, respectively, culminating in a clear set of criteria for an improved interpretation of the END wavefunction along with a derivation used to find the associated important states.