Extending relativistic linear response theory to address solvent effects

The central aim of this thesis is to derive, implement and test new methods to calculate various types of spectroscopies of compounds containing heavy elements in an aqueous environment. Methods that can target such systems have to consider the following:(i) It is crucial to take relativistic effects into account.(ii) Modeling of larger systems is expensive in quantum chemistry. Thus, cheaper options need to be consideredfor the water solvent.(iii) Methods to calculate electronic spectra have to be able to model electronic excitations properly.(i) The relativistic effects can be obtained by solving the Dirac equation. This yields a four-component wave function, but methods based on only two-components have been developed in this thesis. (ii) Larger systems can be tackled by dividing them into a region that is treated by methods from electronic structure theory, and a larger environment that is treated classically as a collection of localized static multipole moments (charges, dipole moments, etc.). In most such hybrid schemes (called QM/MM) we only take into account how the static multipole moments in the environment influence the wave function in the QM region. In this thesis, however, we allow mutual polarization of the regions through the polarizable embedding (PE) model. (iii) We calculate excited state properties through linear response theory. This has been developed to work with a variety of approximate state wave functions and has been extended to a relativistic framework. Moreover, it has been combined with PE. Yet, regular linear response theory suffers from problems in non-resonant regions of spectra. For this, we consider a variant of linear response theory, called the complex polarization propagator. Here, the life-times of the excited states are included in the response equations. This allows the calculation of spectra in regions that are problematic in regular response theory. In this thesis, we have devised a method that combines relativistic CPP within a polarizable embedding framework. We employ the method on light-activated platinum complexes with application in chemotheraphy. Here, both relativistic and solvent effects are crucial to model the excitation processes. Moreover, we also consider the calculation of electronic circular dichroism for chiral organic molecules that contain heavy elements like iodine

The photons payload, G-494: A learning experience

PHOTONS (Photometric Thermospheric Oxygen Nightglow Study) is an optical remote sensing payload developed for Get Away Special (GAS) flight by the National Research Council of Canada. The device is extremely sensitive and is suitable for making measurements of low intensity, aeronomically generated atmospheric emissions in the nadir and the limb and of Shuttle ram glow. The unit uses a sealed canister and UV transmitting viewing ports. During the flight of STS 61-C, PHOTONS received one hour of operation and aeronomic observations were made. Good diagnostic data were obtained and the science part of the experiment malfunctioned. Post flight inspection revealed that the payload was in perfect working order except for total failure of the photomultiplier detectors. The experiment and the payload are described and the flight results are discussed along with the cause of the malfunctions. It is shown that enough was learned from the flight diagnostic data and about the cause of the malfunction to conclude that the engineering flight was successful and that subsequent flight of the PHOTONS payload will be productive

Investigating the influence of relativistic effects on absorption spectra for platinum complexes with light-activated activity against cancer cells

We report the first investigation of relativistic effects on the UV-vis spectra of two prototype complexes for so-called photo-activated chemotherapy (PACT), trans-trans-trans-[Pt(N3)2(OH)2(NH3)2] and cis-trans-cis-[Pt(N3)2(OH)2(NH3)2].In PACT, design of new drugs requires in-depth understanding of the photo-activation mechanisms. A first step is usually to rationalize their UV-vis spectra for which time-dependent density functional theory (TD-DFT) is an indispensable tool. We carried out TD-DFT calculations with a systematic series of non-relativistic(NR), scalar-relativistic (SR), and four-component (4c) Hamiltonians. Large differences are found between spectra calculated within 4c and NR frameworks, while the most intense features (found at higher energies below 300 nm) can be reasonably well reproduced within a SR framework. Yet the underlying transitions can be strongly influenced by spin-orbit coupling introduced in the 4c framework: while this can affect both intense and less intense transitions in the spectra, the effect is most pronounced for weaker transitions at lower energies, above 300 nm. Since the investigated complexes are activated with light of wavelengths above 300 nm, employing a method with explicit inclusion of spin-orbit coupling may be crucial to rationalize the activation mechanism. All calculations were carried out with both the CAM-B3LYP and B3LYP functionals; we generally find the former to perform best in comparison with experimental spectra.Comment: 24 pages, 10 Figures, 1 Table. 25 pages supporting informatio

Computing decay widths of autoionizing Rydberg states with complex-variable coupled cluster theory

We compute autoionization widths of various Rydberg states of neon and dinitrogen by equation-of-motion coupled-cluster theory combined with complex scaling and complex basis functions. This represents the first time that complex-variable methods are applied to Rydberg states represented in Gaussian basis sets. A new computational protocol based on Kaufmann basis functions is designed to make these methods applicable to atomic and molecular Rydberg states. As a first step, we apply our protocol to the neon atom and computed widths of the $3s$, $3p$, $4p$ and $3d$ Rydberg states. We then proceed to compute the widths of the $3s\sigma_g$, $3d\sigma_g$, and $3d\pi_g$ Rydberg states of dinitrogen, which belong to the Hopfield series. Our results demonstrate a decrease in the decay width for increasing angular momentum and principal quantum number within both Rydberg series