Remarkably, an astrophysical black hole has only two attributes: its mass and its spin angular momentum. Spin is often associated with the exotic behavior that black holes manifest such as the production of relativistic and energetic jets. In this thesis, we advance one of the two primary methods of measuring black hole spin, namely, the continuum-fitting method by (1) improving the methodology; (2) testing two foundational assumptions; and (3) measuring the spins of two stellar-mass black holes in X-ray binary systems. Methodology: We present an empirical model of Comptonization that self-consistently generates a hard power-law component by upscattering thermal accretion disk photons as they traverse a hot corona. We show that this model enables reliable measurements of spin for far more X-ray spectral data and for more sources than previously thought possible. Testing the foundations: First, by an exhaustive study of the X-ray spectra of LMC X–3, we show that the inner radius of its accretion disk is constant over decades and unaffected by source variability. Identifying this fixed inner radius with the radius of the innermost stable circular orbit in general relativity, our findings establish a firm foundation for the measurement of black hole spin. Secondly, we test the customary assumption that the inclination angles of the black-hole’s spin axis and the binary’s orbital axis are the same; for XTE J1550–564 we show that they are aligned to within \(12^{\circ}\) by modeling the kinematics of the large-scale jets of this microquasar. Measuring spins: We have made the first accurate continuum-fitting spin measurements of the black hole primaries in H1743–322 and XTE J1550–564. For this latter black hole, we have also measured its spin using the other leading method, namely, modeling the broad red wing of the \(Fe K\alpha\) line. As we show, these two independent measurements of spin are in agreement. / Astronomy

Water is a complex liquid with many unusual properties. Our understanding of its physical, chemical and biological properties is greatly advanced after a century of dedicated research but there are still many unresolved questions. If answered, they could have important long-term consequences for practical applications ranging from drug design to water purification. This thesis presents results on the structure, dynamics and thermodynamics of liquid water. The focus is on theoretical simulations applied to interpret experimental data from mainly x-ray and neutron scattering and spectroscopy techniques. The structural sensitivity of x-ray and neutron diffraction is investigated using reverse Monte Carlo simulations and information on the pair-correlation functions of water is derived. A new method for structure modeling of computationally demanding data sets is presented and used to resolve an inconsistency between experimental extended x-ray absorption fine-structure and diffraction data regarding oxygen-oxygen pair-correlations. Small-angle x-ray scattering data are modeled using large-scale classical molecular dynamics simulations, and the observed enhanced scattering at supercooled temperatures is connected to the presence of a Widom line emanating from a liquid-liquid critical point in the deeply supercooled high pressure regime. An investigation of inherent structures reveals an underlying structural bimodality in the simulations connected to disordered high-density and ordered low-density molecules, providing a clearer interpretation of experimental small-angle scattering data. Dynamical anomalies in supercooled water observed in inelastic neutron scattering experiments, manifested by low-frequency collective excitations resembling a boson peak, are investigated and found to be connected to the thermodynamically defined Widom line. Finally, x-ray absorption spectra are calculated for simulated water structures using density functional theory. An approximation of intra-molecular zero-point vibrational effects is found to significantly improve the relative spectral intensities but a structural investigation indicates that the classical simulations underestimate the amount of broken hydrogen bonds. / Vatten är en komplex vätska med flera ovanliga egenskaper. Vår förståelse av dess fysiska, kemiska och biologiska egenskaper har utvecklats mycket sedan systematiska vetenskapliga studier började genomföras för mer än ett sekel sedan, men många viktiga frågor är fortfarande obesvarade. En ökad förståelse skulle på sikt kunna leda till framsteg inom viktiga områden så som medicinutveckling och vattenrening. Denna avhandling presenterar resultat kring vattnets struktur, dynamik och termodynamik. Fokusen ligger på teoretiska simuleringar som använts för att tolka experimentella data från huvudsakligen röntgen- och neutronspridning samt spektroskopier. Den strukturella känsligheten i röntgen- och neutrondiffraktionsdata undersöks via reverse Monte Carlo metoden och information om de partiella parkorrelationsfunktionerna erhålls. En ny metod för strukturmodellering av beräkningsintensiva data presenteras och används för att lösa en motsägelse mellan experimentell diffraktion och EXAFS angående syre- syre parkorrelationsfunktionen. Data från röntgensmåvinkelspridning modelleras med storskaliga klassiska molekyldynamiksimuleringar, och den observerade förhöjda småvinkelspridningen vid underkylda temperaturer kopplas till existensen av en Widomlinje härrörande från en vätske- vätske kritisk punkt i det djupt underkylda området vid höga tryck. En undersökning av inherenta strukturer i simuleringarna påvisar en underliggande strukturell bimodalitet mellan molekyler i oordnade högdensitetsregioner respektive ordnade lågdensitetsregioner, vilket ger en tydligare tolkning av den experimentella småvinkelspridningen. Dynamiska anomalier i underkylt vatten som har observerats i inelastisk neutronspridning, speciellt förekomsten av lågfrekventa excitationer som liknar en bosontopp, undersöks och kopplas till den termodynamiskt definierade Widomlinjen. Slutligen presenteras densitetsfunktionalberäkningar av röntgenabsorptionsspektra för simulerade vattenstrukturer. En approximation av intramolekylära nollpunktsvibrationseffekter förbättrar relativa intensiteteri spektrumen avsevärt, men en strukturanalys visar att klassiska simuleringar av vatten underskattar andelen brutna vätebindningar. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 6: Submitted. Paper 7: Submitted. Paper 8: Manuscript. Paper 9: Submitted.

Nowadays, material, energy and information technologies are three pillar industries. The materials that have close relation with our life have also been the foundation for the development of energy and information technologies. As the new member of the material family, functional molecular materials have become increasingly important for many applications, for which the design and characterization by the theoretical modeling have played the vital role. In this thesis, three different categories of functional molecular materials, the endohedral fullerenes, the fullerene derivatives and the self-assembled monolayers (SAMs), have been studied by means of first principles methods. The non-metal endohedral fullerene N@C60 is a special endohedral fullerene that is believed to be relevant to the construction of future quantum computer. The energy landscape inside the N@C60 has been carefully explored by density functional theory (DFT) calculations. The most energy favorable potential energysurfaces (PESs) for the N atom to move within the cavity have been identified. The effect of the charging on the PESs has also been examined. It is found that the inclusion of dispersion force is essential in determining the equilibriumstructure of N@C60. Furthermore, the performance of several commonly useddensity functionals with or without dispersion correction has been verified for ten different endohedral fullerenes A@C60 with the atom A being either reactive nonmetal or nobel gases elements. It shows that the inclusion of the dispersion forcedoes provide better description for the binding energy (BE), however, none ofthem could correctly describe the energy landscape inside all the ten endohedral fullerenes exclusively. It thus calls for the further improvement of current density functionals for weak interacting systems. Soft X-ray spectroscopy is a powerful tool for studying the chemical and electronic structures of functional molecular materials. Theoretical calculations have been proven to be extremely useful for providing correct assignments for spectraof large systems. In this thesis, we have performed first principles simulations forthe near-edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectra (XPS) of fullerene derivatives and aminothiolates SAMs. Our calculatedspectra can accurately reproduce experimental results available for all the systemsunder investigations, and identify the species or structures that are responsible for those unexpected spectral features observed in experiments. We have suggested a modified building block (MBB) approach that allows to calculate NEXAFS spectraof a large number of fullerene derivatives with very small computational cost, and resolved the long standing puzzle around the experimental XPS and NEXAFS spectra of SAMs with aminothiolates. / <p>QC 20120523</p>

Multiconfigurational quantum chemistry methods, and especially the multiconfigurational self-consistent field (MCSCF) and multireference perturbation theory (MRPT2), are powerful tools, particularly suited to the accurate modeling of photochemical processes and transition metal catalysis. However, they are limited by their high computational cost compared to other methods, especially density functional theory. Moreover, there are areas where they would be expected to perform well, but where they are not applied due to lack of experience. This thesis addresses those issues. First, the efficiency of the Cholesky decomposition approximation to reduce the cost of MCSCF and MRPT2 without sacrificing their accuracy is demonstrated. This then motivates the extension of the Cholesky approximation to the computation of MCSCF nuclear gradients, thus strongly improving the ability to perform MCSCF non-adiabatic molecular dynamics. Typically, a tenfold speed-up is observed allowing dynamic simulation of larger systems or over longer times. Finally, multiconfigurational methods are applied to the computation of X-ray spectra of transition metal complexes. The importance of the different parameters in the calculation is systematically investigated, laying the base for wider applications of those accurate methods in the modeling of X-ray spectroscopy. A tool to analyze the resulting spectrum in terms of molecular orbitals is also presented, strengthening the interplay between theory and experiments. With these developments and other significant ones that have happened in recent years, multiconfigurational methods can now reach new grounds and contribute to important new discoveries

No description available.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1973. / Bibliography: leaves [293]-300. / xvi, 300 l illus., tables

The present thesis is devoted to theoretical studies of pulse propagation of light through linear and nonlinear media, and of light-induced nuclear dynamics. The first part of the thesis addresses propagation of light pulses in linear periodical media - photonic crystals. The main accent was put on studies of the angular properties of two qualitatively different types of photonic crystals: holographic photonic crystals, and impurity band based photonic crystals. The anisotropy of band structure, group velocity and pulse delay with respect to the light polarization are analyzed. In the second part of the thesis a strict theory of nonlinear propagation of a few strong interacting light beams is presented. The key idea of this approach is a self-consistent solution of the nonlinear wave equation and the density matrix equations of the material. This technique is applied to studies of dynamics of cavityless lasing generated by ultra-fast multi-photon excitation. It is shown that interaction of co- and counter-propagating pulses of amplified spontaneous emission (ASE) affects the dynamics and efficiency of nonlinear conversion. Our dynamical theory allows to explain the asymmetric spectral properties of the forward and backward ASE pulses, which were observed in recent experiment with different dye molecules. It is shown that the ASE spectral profile changes drastically when the pump intensity approaches the threshold level. The effect of the temporal self-pulsation of ASE is studied in detail. The third part of the thesis is devoted to light-induced nuclear dynamics. Time- and frequency-resolved X-ray spectroscopy of molecules driven by strong and coherent infrared (IR) pulses shows that the phase of the IR field strongly influences the trajectory of the nuclear wave packet, and hence, the X-ray spectrum. Such a dependence arises due to the interference of one (X-ray) and two-photon (X-ray + IR) excitation channels. The phase of the light influences the dynamics also when the Rabi frequency approaches the vibrational frequency, breaking down the rotating-wave approximation. The probe X-ray spectra are also sensitive to the delay time, the duration, and the shape of the pulses. The evolution of the nuclear wave packets in the dissociative core-excited state affects the dynamics of resonant Auger scattering from fixed-in-space molecules. One of the important dynamical effects is the atomic-like resonance which experiences electronic Doppler shift. We predict that the scattering of the Auger electrons by nearby atoms leads to new Doppler shifted resonances. These extra resonances show sharp maxima in the bond directions, which makes them very promising as probes for local molecular structure using energy and angular resolved electron-ion coincidence techniques. Our theory provides prediction of several new effects, but also results that are in good agreement with the available experimental data. / QC 20100906

Thesis (M.S.)--University of Alabama at Birmingham, 2007. / Additional advisors: Peter G. Anderson, Brigitta C. Brott, Jack E. Lemons. Description based on contents viewed Feb. 4, 2008; title from title screen. Includes bibliographical references (p. 69-70).

Thesis (Ph.D.) -- McMaster University, 1999. / Includes bibliographical references (leaves 212-219). Also available via World Wide Web.

Diss. (sammanfattning). Umeå : Sveriges lantbruksuniv. / Härtill 4 uppsatser.