Development and Application of Second-Order Methods for UV-VIS Spectroscopy of Organic Molecules

Ultraviolet–Visible (UV–VIS) spectroscopy is one of the oldest experimental techniques, which nowadays plays one of the most important roles in state-of-the-art areas of modern natural science, such as: investigation of energy-transfer processes in biological molecules; development of renewable energy resources and new technologies for solar energy conversion and storage; prediction of properties of (bio-)molecules and drug design; investigation of excited-state dynamics of molecules and materials, as well as other applications.

As a result of such huge impact, UV–VIS spectroscopy has been intensively developed in the last decades. This has led to the appearance of complex experimental techniques like, for example, Pump-Probe and Transient Absorption spectroscopies, whereas the interpretation of experimental data obtained from such sophisticated techniques is not straightforward. Indeed, with the increasing complexity of experimental techniques, the intricacy of experimental data has been rising proportionally. Therefore, the correct understanding of the experimental data requires proper theoretical tools and efficient computational techniques for its simulation and further detailed analysis.

Today, there is a multitude of computational methods, which make it possible to simulate different molecular properties with chemical accuracy or even higher. However, the computational cost of such simulations is usually in inverse ratio to both accuracy and size of the molecular system, which renders many existing methods inapplicable for biological macromolecules.

This thesis introduces extensions of existing methodologies for the simulation of molecular spectra, with a particular focus on applicability to large molecular systems. It is based on extensive studies devoted to the derivation, implementation, and application of new theoretical approaches to simulate spectroscopic phenomena in the UV–VIS region of organic/biological molecules, as well as benchmarking of existing methods.

The thesis is based on three projects, each focused on a specific spectroscopic area: derivation and implementation of first-principle computational methods for simulation of Electronic Circular Dichroism and One-Photon Absorption phenomena within a Coupled Cluster framework; extension of the portfolio of the Algebraic Diagrammatic Construction spectroscopies to Magnetic Circular Dichroism; investigation of existing computational schemes for the simulation of Transient Absorption of nucleobases in gas-phase and solution.