Theoretical studies of response properties of organic molecules

Sammanfattning: In this thesis eight papers are presented. They represent development of theory and implementation technique in quantum chemistry, as well applications. The first two papers describe advances in geometry optimization techniques. In the first of these papers a technique for achieving an approximate curvature description of the energy surface is presented and in the next a technique for inter molecular optimization. Paper three presents a solvation description of methylen peroxide, an intermediate in ozonolysis of ethene. The fourth paper describes a direct implementation of calculation of vibrational properties. Paper five describes a technique for accurately calculating the vibronic resolution of spectra. This technique was applied on the lowest forbidden transitions in benzene, with excellent agreement with experiments. In paper six an experimental IR-spectrum of an intermediate in the formation of perchloric acid was compared with a theoretical IR-spectra. By using the shifts that occur during the reaction, the reaction path was possible to determine. The Bergman reaction and the related topic of the relative energies of the benzynes were treated in paper seven and eight.