This thesis deals with the weak interaction between the electronic and degenerate vibrational motions in linear polyatomic molecules. Second-order vibronic energy expressions are obtained for triatomic and tetratomic molecules in degenerate electronic states. / Thesis / Doctor of Philosophy (PhD)

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Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第16874号 / 工博第3595号 / 新制||工||1543(附属図書館) / 29549 / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 田中 一義, 教授 佐藤 啓文, 教授 梶 弘典 / 学位規則第4条第1項該当

The Born-Oppenheimer approximation is a mainstay in molecular physics and chemistry and can be considered a two step process. The first step is to solve the electronic problem with nuclei fixed in space while the second step is to then determine the nuclear dynamics on a given electronic potential energy surface. This first-step calculation of the wavefunction and electronic energies for fixed nuclei has been at the center of modern quantum chemistry for decades. While the majority of chemical processes can be investigated by considering these single electronic surface dynamics, there exist problems in which the dynamics are not constrained to a single electronic surface. One such problem that justifies going beyond the typical adiabatic approximation is the determination of energy levels in systems with strongly coupled electronic states. While some work has been done using diabatic or quasidiabatic Hamiltonians to describe such systems, the work has historically been of qualitative accuracy. Model Hamiltonians have been constructed using experimental data to help calibrate the model parameters aided by the use of lower level adiabatic calculations to help inform the model. It is only within the last few years that theorists have been able to attempt parameterization of such models using only ab initio methods. The goal of this work is to develop a computational framework for the parameterization of quantitatively accurate quasidiabatic Hamiltonians based purely on ab initio information and apply it to a notoriously difficult problem that has plagued the theoretical community for decades -- high accuracy treatment of the energy levels of the NO₃ radical. In this dissertation, high-level ab initio calculations that employ the equation-of-motion coupled-cluster method in the single, doubles and triples (EOMIP-CCSDT) have been used in conjunction with a quasidiabatic ab initio approximation to construct a vibronic Hamiltonian for the strongly coupled X²A'₂ and B²E' states of the NO₃ radical. A quartic vibronic coupling model potential of the form advocated by Köppel et al. has been used to determine the energy levels of this system to quantitative accuracy when compared to experimental data. In order to obtain sufficiently accurate potential energy surfaces necessary to parameterize a quantitatively accurate model Hamiltonian, thousands of large calculations had to be run that do not fit in memory on even the largest HPC systems. The resulting large, out-of-core solves do not map to traditional systems in a way to enable any reasonable parallelization. As a result, a new MPI-based utility has been developed to support out-of-core methods on distributed memory systems. This and other advances in scientific computing form the basis of the developed computational framework. / text

Understanding the properties of electronically interacting molecular chromophores, which involve internally coupled electronic-vibrational motions, is important to the spectroscopy of many biological systems. Here we apply linear absorption, circular dichroism, and two-dimensional fluorescence spectroscopy to study the local structure and excited state dynamics of excitonically coupled cyanine dimers that are rigidly positioned within the sugar-phosphate backbones of the DNA. Dimer probes were positioned within the double-stranded DNA duplex and at the single-strand/double-stranded DNA junction to examine the positional dependence of the structural variation and fluctuations. We interpret spectroscopic measurements in terms of the Holstein vibronic dimer model, from which we obtain information about the local conformation of the dimer probe locally within their respective DNA environments. We show that the exciton-coupling strength of the dimer-DNA construct can be systematically varied with temperature below the double-stranded – single-strand DNA denaturation transition. Using time-resolve 2DFS measurements we observed long lived vibronic coherences in the system. The properties of the cyanine DNA construct we determine suggest that it may be employed as a useful model system to test fundamental concepts of protein DNA interactions and the role of electronic-vibrational coherence in electronic energy migration within exciton-coupled biomolecular arrays. This dissertation contains previously published and unpublished co-authored material.

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Transient molecules are of great importance due to their critical role as intermediates in the semiconductor industry, in upper atmosphere reactions, and in astrochemistry. In the present work, reactive intermediates were produced in the laboratory by applying an electric discharge through a suitable precursor gas mixture and studied by means of their laser-induced fluorescence and emission spectra. The band systems of and have been studied in detail. The energy levels of both isotopologues were fitted with a Renner-Teller model, and the isotope relations have been used to test the validity of the derived parameters. The A2Πu - X 2Πg electronic transition of jet-cooled has been detected and shown to originate from the Ω=3/2 spin-orbit component of v=0 of the ground state. For the first time, the 0-0 band has been identified and vibrational assignments have been made. Our ab initio studies show that the extensive observed perturbations are due to spin-orbit interaction between A2Πu(3/2) and B2Δu(3/2) states. The experimental data were fitted to an effective Hamiltonian and yielded the spin-orbit coupling term =240 cm-1. LIF and emission spectra of the transition of N2O+ have been recorded. Both spin-orbit components of the band were studied at high resolution and rotationally analyzed, providing precise molecular constants. Emission spectra provided extensive data on the ground state vibrational levels which were fitted to a Renner-Teller model including spin-orbit and Fermi resonance terms. The previously unknown electronic spectrum of the H2PO radical has been identified. Ab initio predictions were used to aid in the analysis of the data. The band system is assigned as the electronic transition. The excited state molecular structure was determined by rotational analysis of high resolution LIF spectra. The band systems of the HBCl and DBCl free radicals have been studied in detail. This electron promotion involves a linear-bent transition between the two Renner-Teller components of what would be a 2Π electronic state at linearity. Ab initio potential energy surface calculations were used to help in assigning the LIF spectra which involve transitions from the ground state zero-point level to high vibrational levels of the excited state.

C’est dernières années, les progrès des techniques expérimentales combinées avec les simulations théoriques ont données un accès à l’étude et le contrôle des réactions photochimiques dans des systèmes moléculaires de grande taille. Ceci ouvre des portes à de nouvelles applications technologiques. Par exemple, les molécules de la famille du 3-hydroxychromone et de l’aminobenzonitrile sont des types de systèmes où les spectres de fluorescences vont présentés des différences importantes suivant l’environnement du système ou même suivant les substituants utilisés. Ce type de propriété est crucial dans le domaine des matériaux organique, afin de pouvoir comprendre et designer des matériaux qui présentent des propriétés optiques choisis tells que les marqueurs fluorescents dans le domaine médical par exemple.Notre stratégie pour étudier la réactivité photochimique est la suivante: *Explorer la surface d’énergie potentielle et optimiser les points spécifiques avec des calculs de chimie quantiques. Dans un premier temps, on a utilisé des méthodes CASSCF/CASPT2 et la méthode PCM pour décrire les effets de solvant. * Génération des surfaces d énergies potentielles exprimer sous la forme de fonctions analytiques des coordonnées nucléaires. * Résolution de l’équation de Schrödinger dépendant du temps pour les noyaux et pour tout les derges de libertés de la molécule. Cette étape est faite à l’aide de la méthode multilayer multiconfiguration time-dependent hartree (ML-MCTDH). / Over the last decades, progress in experimental techniques combined with theoretical simulations has given access to studying and controlling the photochemical reactivity of large molecular systems with numerous technological applications. 3-hydroxychromone and aminobenzonitrile-like molecules are an example where different fluorescence patterns are observed, depending of the solvent or its substituents. Such properties are crucial in the field of organic materials to understand and design materials with specific optical properties such as fluorescent markers.Our strategy to study the photochemistry reactivity is summarised as follows: * Exploring the potential energy surfaces and optimising specific points with quantum chemistry calculations. In a first stage, these are run at the CASSCF/CASPT2 level of theory with a polarised extended basis set, and the solvent effect is described implicitly with the PCM model. * Generating the full dimension potential energy surfaces as analytical functions of the nuclear coordinates.* Solving the nuclear time-dependent Schrödinger equation for all the degrees of freedom. This is achieved with the multilayer Multi-Configuration Time-Dependent Hartree method (ML-MCTDH).

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18288号 / 工博第3880号 / 新制||工||1595(附属図書館) / 31146 / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 田中 一義, 教授 田中 庸裕, 教授 佐藤 啓文 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19741号 / 工博第4196号 / 新制||工||1647(附属図書館) / 32777 / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 田中 庸裕, 教授 佐藤 啓文, 教授 梶 弘典 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM