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Abstract

This dissertation deals with theoretical methods to simulate the linear and nonlinear absorption of circularly polarized light. Specifically, expressions for the rotatory strength in the intermediate state representation (ISR) of the algebraic-diagrammatic construction (ADC) scheme up to third order are detailed in both the length and velocity gauge, and are used to simulate electronic circular dichroism (ECD) spectra. The well-known origin-dependence inherent to the prediction of magnetic properties within approximate theories is explored related to ECD using the ADC method. The ECD spectra of methyloxirane, methylthiirane and their dimethylated counterparts, H2O2 and H2S2 are calculated at the ADC(2) and ADC(3) levels of theory and compared to the same spectra calculated at CC2, CCSD and CC3 level of theory. The simulated ECD spectra of the bicyclic ketones, camphor, norcamphor and fenchone are analysed at ADC(3) level and compared against experimental gas-phase ECD spectra. Solvent effects are addressed by the use of a polarizable continuum model (PCM) on the simulated ECD spectra of solvated epinephrine. The time-resolved counterpart to ECD, namely excited-state electronic circular dichroism (ESECD) is further derived within the ADC/ISR formalism, replacing the ground state with an excited-state, to obtain excited-state rotatory strengths. The quality of the simulated ESECD spectra of norcamphor at ADC(3) level is compared with those same spectra calculated at time-dependent density functional theory (TDDFT) with several exchange-correlation functionals. Furthermore, the ESECD spectrum of binol in the energetically lowest singlet excited state (S1-ESECD) is computed at the ADC(2) level of theory. The simultaneous absorption of two-photons where at least one of them is circularly polarized, so-called “two-photon circular dichroism” (TPCD), is derived within the ADC/ISR formalism. In this case, three formulations of the TPCD rotatory strength are employed and used to simulate the TPCD spectra of methyloxirane and methylthiirane. The chiroptical properties of a twisted biphenyl molecule is subsequently evaluated in terms of their linear (ECD) and nonlinear (TPCD) spectra. The impact the polarization- propagation of the two light beams have on the simulated TPCD spectra of norcamphor is further demonstrated. Next, expressions for the first-order hyperpolarizability are derived and used to calculate the second harmonic generation (SHG) and hyper-Rayleigh scattering (HRS) within the ADC/ISR formalism. The static first-order hyperpolarizability of several organic and inorganic molecules is then compared at ADC(n) and CC levels of theory. The dynamic, SHG, signal strength of several molecules is subsequently evaluated at ADC(n) levels of theory with respect to experimental measurements. Lastly, the HRS of ammonia is evaluated at ADC(2) and ADC(3) levels of theory.