%0 Generic
%A Krauter, Caroline Maria Magdolna
%D 2014
%F heidok:16696
%R 10.11588/heidok.00016696
%T Development, Benchmarking, and Applications of Efficient  Theoretical Approaches for the Calculation of Excited States in Organic Systems
%U https://archiv.ub.uni-heidelberg.de/volltextserver/16696/
%X Processes initiated by photoexcitation play an important role in many biological systems as well as in technical applications. A whole variety of quantum chemical methods for the treatment of such excited states has been developed over the past years. However, many are either restricted to small or medium-sized systems or only applicable to certain types of electronic excitations. Therefore, the development of efficient quantum chemical excited states methods is one of the central aspects of modern theoretical chemistry.     In this work, different excited state approaches within the algebraic diagrammatic construction (ADC) family of methods were derived and implemented. First, the scaled-opposite spin approximation was used to develop a variant of the extended ADC(2) methods that allows for an improved  treatment of doubly excited states at reduced computational cost. Additionally, the generation of spin-orbit coupling elements based on an atomic mean-field approach was implemented for the whole hierarchy of ADC methods up to third order. Test calculations and comparison with existing methods revealed very good results. Last but not least, a scaling approach for the identification of plasmons in molecules previously introduced for TDDFT has been adopted to the ADC methods. Such plasmons are of great importance in the field of organic electronics. Here, the scaling approach was shown to work efficiently for a series of linear polyenes. All three theoretical methods were implemented in a development version of the adcman module of the Q-Chem program package. Thereby, the functionality of this module has been further extended making it applicable to a wider range of molecular systems and photochemical problems. Finally, ADC methods were used in combination with experimental results to successfully unravel the photochemical relaxation network of coumarin derivatives which turned out to incorporate two parallel radiationless relaxation pathways.