@article{PericEngels1992, author = {Peric, M. and Engels, Bernd}, title = {Ab initio calculations of the vibronically averaged values for the hyperfine coupling constants in NH\(_2\), NHD and ND\(_2\)}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58941}, year = {1992}, abstract = {Vibronically averaged values for K =0 and K = 1 bending levels in the energy range between 0 and 25 000 cm\(^{-1}\) are computed for the \(^{14}\)N, H, and D atoms in NH\(_2\), NHD, and ND\(_2\) The pure ab initio electronic potentials, as well as those derived by fitting of experimentally observed band positions are employed. Effects of vibronic coupling and local perturbations of close-lying levels belanging to different electronic states are discussed.}, subject = {Organische Chemie}, language = {en} } @article{StaikovaEngelsPericetal.1993, author = {Staikova, M. and Engels, Bernd and Peric, M. and Peyerimhoff, S. D.}, title = {Ab initio calculation of the vibronically averaged hyperfine coupling constants in the two lowest electronic states of H\(_2\)O\(^+\)}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58998}, year = {1993}, abstract = {No abstract available}, subject = {Organische Chemie}, language = {en} } @article{PericEngels1992, author = {Peric, M. and Engels, Bernd}, title = {Ab initio calculation of the vibronically averaged hyperfine coupling constants in the 1\(^2\)Π\(_u\) electronic state of CH\(_2 ^+\)}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58951}, year = {1992}, abstract = {The results of pure ab initio calculations of the hyperfine coupling constants for the 1 \(^2 \pi _u\) electronic state for various isotopomers of CHi in the energy range between 0 and 20 000 cm\(^{-1}\) are presented. Effects of vibronic and spin-orbit coupling are discussed.}, subject = {Organische Chemie}, language = {en} } @article{SuterHuangEngels1994, author = {Suter, H. U. and Huang, M.-B. and Engels, Bernd}, title = {A Multireference Configuration Interaction Study of the Hyperfine Structure of the Molecules CCO, CNN and NCN in their triplet ground states}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-59108}, year = {1994}, abstract = {The hyperfine structures of the isoelectronic molecules CCO. CNN, and NCN in their triplet ground states (X\(^3 \sum ^-\)) are investigated by means of ab initio methods. The infrared frequencies and geometries are detennined and compared with experiment. Configuration selected multireference configuration interaction calculations in combination with perturbation theory to correct the wave function (MRD-CI/B\(_K\)) employing extended atomic orbital (AO) basis sets yielded very accurate hyperfine properties. The theoretical values for CCO are in excellent agreement with the experimental values determined by Smith and Weltner [J. Chem. Phys. 62,4592 (1975)]. For CNN, the first assignment of Smith and Weltner for the two nitrogen atoms has to be changed. A qualitative discussion of the electronic structure discloses no simple relation between the structure of the singly occupied orbitals and the measured hyperfine coupling constants. Vibrational effects were found to be of little importance.}, subject = {Organische Chemie}, language = {en} } @article{FroudakisZdetsisMuehlhaeuseretal.1994, author = {Froudakis, G. and Zdetsis, A. and M{\"u}hlh{\"a}user, M. and Engels, Bernd and Peyerimhoff, S. D.}, title = {A comparative ab initio study of the Si\(_2\)C\(_4\), Si\(_3\)C\(_3\), Si\(_4\)C\(_2\) clusters}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-59097}, year = {1994}, abstract = {Various structural possibilities for the Si\(_2\)C\(_4\) and Si\(_4\)C\(_2\) clusters are investigated by employing a basis set of triple-zeta plus polarization quality; electron correlation is generally accounted for by second-order M0ller-Plesset and, in certain instances, by higher-order perturbation (CASPT2) approaches. The building-up principle recently suggested from an analysis of Si\(_3\)C\(_3\) clusters is found to be fully operative for Si\(_2\)C\(_4\) and Si\(_4\)C\(_2\) clusters. A comparison of the structure and stability of various geometrical arrangements in the series C\(_6\) , Si\(_2\)C\(_4\) , Si\(_3\)C\(_3\) , Si\(_4\)C\(_2\), and Si\(_6\) shows that linear and planar structures become rapidly less stable if carbons are replaced by silicons and that the three-dimensional bipyramidal forms become less favorable as soon as silicons are exchanged by carbons in the parent Si\(_6\) structure. The effects can be rationalized in qualitative terms based on differences in silicon and carbon bonding.}, subject = {Organische Chemie}, language = {en} } @article{ChristlWarrenHawkinsetal.1973, author = {Christl, Manfred and Warren, J. D. and Hawkins, B. L. and Roberts, J. D.}, title = {\(^{13}\)C and \(^{15}\)N Nuclear Magnetic Resonance Spectroscopy of Nitrile Oxides and Related Reaction Products : Unexpected \(^{13}\)C and \(^{15}\)N Nuclear Magnetic Resonance Parameters of 2,4,6-Trimethylbenzonitrile Oxide}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-57894}, year = {1973}, abstract = {No abstract available}, subject = {Organische Chemie}, language = {en} } @article{ChristlBrunnRothetal.1989, author = {Christl, Manfred and Brunn, E. and Roth, W. R. and Lennartz, H.-W.}, title = {7-Methyl- and 7-Phenylcyclohepta-1,3,5-trienes from Benzvalene Via 3,3a,4,5,6,6a-Hexahydro-4,5,6-methenocyclopentapyrazoles and Tetracyclo[4.1.0.0\(^{2,4}\).0\(^{3,5}\)]heptanes}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58471}, year = {1989}, abstract = {No abstract available}, subject = {Organische Chemie}, language = {en} } @article{ChristlBraunMueller1992, author = {Christl, Manfred and Braun, Martin and M{\"u}ller, Germar}, title = {1,2,4-Cyclohexatriene, an Isobenzene, and Bicyclo[4.4.0)deca-1,3,5,7,8-pentaene, an Isonaphthalene: Generation and Trapping Reactions}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58639}, year = {1992}, abstract = {No abstract available}, subject = {Organische Chemie}, language = {en} }