Excited state mixed valence (ESMV) occurs in molecules in which the ground state has a symmetrical charge distribution but the excited state possesses two or more interchangeably equivalent sites that have different formal oxidation states. Although mixed valence excited states are relatively common in both organic and inorganic molecules, their properties have only recently been explored, prim...

Steady-state and time-resolved emission spectroscopy are valuable tools to probe photochemical processes of metal-ligand, coordination complexes. Ru(II) polyazine light absorbers are efficient light harvesters absorbing in the UV and visible with emissive ³MLCT excited states known to undergo excited state energy and electron transfer. Changes in emission intensity, energy or band-shape, as wel...

Bacteriochlorophylls (BChls) play an important role as light harvesters in photosynthetic bacteria. Interestingly, bacteriochlorophylls (BChls) a, b, and g selectively tune their visible (Qx) and near IR (Qy) absorption bands by the substituent changes. In this paper, we theoretically study the mechanism for the selective control of the absorption bands. Density functional theory (DFT) and time...

We have performed ab initio CASSCF, CASPT2, and EOM-CCSD calculations on doubly deprotonated p-coumaric acid (pCA(2-)), the chromophore precursor of the photoactive yellow protein. The results of the calculations demonstrate that pCA(2-) can undergo only photoisomerization of the double bond. In contrast, the chromophore derivative with the acid replaced by a ketone (p-hydroxybenzylidene aceton...

Time-resolved infrared (TR-IR) absorption spectroscopy in both the femtosecond and nanosecond time domain has been applied to examine the photolysis of benzoic acid in acetonitrile solution following either 267 nm or 193 nm excitation. By combining the ultrafast and nanosecond TR-IR measurements, both the excited states and the photofragments have been detected and key mechanistic insights were...

We extend the Eckart theorem, from the ground state to excited states, which introduces an energy augmentation to the variation criterion for excited states. It is shown that the energy of a very good excited state trial function can be slightly lower than the exact eigenvalue. Further, the energy calculated by the trial excited state wave function, which is the closest to the exact eigenstate ...

The Shockley-Read-Hall rate equations determine the average carrier transitions via a single-level defect in the band gap of a nondegenerate semiconductor. In the present work the differential rate equations for multiple levels, or localized states systems, are derived from first principles. These multiple level systems comprise the multiple discrete defects system and the coupled or excited st...

Cu(I)-phenanthrolines are an important class ofmetal-organicmolecules that exhibitsmuch promise for solar energy harvesting and solar-driven catalysis applications. Although many experimental studies have been performed calling for high-level simulations to elucidate their photophysics, a complete picture is still missing. This is the goal of the present thesis. On the ultrafast (femtosecond) t...

We develop a resonance theory to describe the evolution of open systems with time-dependent dynamics. Our approach is based on piecewise constant Hamiltonians: we represent the evolution on each constant bit using a recently developed dynamical resonance theory, and we piece them together to obtain the total evolution. The initial state corresponding to one time-interval with constant Hamiltoni...